USABO (USA Biology Olympiad): 2027 Study Guide + Resources
Updated: Aug 28
Updated: 27th August, 2026
TL;DR
The USABO is a four-round national biology competition run by the Center for Excellence in Education (CEE), open to US students in grades 9-12 (homeschoolers included) for a $125 school registration fee, with the 2027 cycle's final registration deadline set for November 15, 2026 and the Open Exam expected in late January or early February 2027. You'll take a 50-minute multiple-choice Open Exam first, and if you score in the top 10%, you move to a 120-minute Semifinal Exam; the top 20 scorers nationally are invited to an in-person National Finals at Harvard University, and the top 4 represent the US at the International Biology Olympiad (2027 IBO is in Warsaw, Poland). There's no cash prize, but a strong USABO result is one of the more recognizable biology credentials you can put in front of a college admissions officer. If you want feedback on how a USABO result fits into your broader application strategy, or you're looking for a research mentor to pair with your Olympiad prep, Lumiere's research program matches students with PhD mentors for exactly that kind of one-on-one guidance.
The USA Biolympiad (USABO) is one of the most competitive science exams you can take in high school. If you're serious about biology, going through the process of preparing for it will push you well past your school curriculum, whether or not you make it to the later rounds.
This blog walks you through what the USABO actually tests, who can compete, the full 2027 cycle timeline, and how to build a study plan that actually moves your score. We'll also point you to real past exams and practice resources instead of vague "study hard" advice.
What is the USABO?
The USABO launched in 2002 and is run by the Center for Excellence in Education (CEE), a nonprofit that also runs the Research Science Institute (RSI). Its goal is to give you a rigorous, standardized way to test your biology knowledge against thousands of students nationally, then internationally.
You'll be tested on both theory and lab skills, through multiple-choice questions, short answers, and (if you advance far enough) hands-on practical rounds. Around 12,000 students register each year. The four gold medalists from the 2026 National Finals represented the US at the 2026 International Biology Olympiad in Vilnius, Lithuania.
Who is eligible for the USABO?
Here's what you need to know before you register, individually or through your school:
You must be in grades 9 through 12. High school seniors are eligible as long as they haven't formally enrolled in an undergraduate program yet.
You register through your school. If your school hasn't participated before, your teacher or coordinator can register directly through USABO.
Your school pays a $125 registration fee to activate your account. Some schools ask students to cover part or all of this. There's also an optional 10% processing fee (about $12.50) charged by the payment processor, Blackbaud, that you can decline during checkout.
Homeschooled students are welcome, but you need to make arrangements before registration closes to test at a local high school or CEE-authorized test center. You may be responsible for the $125 fee.
Citizenship: the Open Exam itself does not require US citizenship or a green card, per CEE's official exam-format page. CEE's separate eligibility page lists citizenship/permanent residency as a blanket requirement without that carve-out, so if you're an international student or on a visa, confirm directly with your school's USABO coordinator before you register, since the two official pages don't currently agree with each other. Citizenship or a green card is unambiguously required starting at the Semifinal Exam.
USABO vs USNCO - which is better?
It depends on your subject focus! If you're weighing the USABO against an olympiad in chemistry, it's worth reading our breakdown of how the U.S. National Chemistry Olympiad (USNCO) compares.
How the USABO is structured: all four rounds explained
The USABO runs in four rounds each year:
Round 1: Open Exam. A 50-minute, proctored, multiple-choice exam administered at your school. The exact number of questions isn't published on CEE's current official exam page. There's no penalty for guessing, so you should never leave a question blank. Citizenship isn't required for this round.
Round 2: Semifinal Exam. If you score in the top 10% of the Open Exam, you move to a 120-minute exam with three parts: Part A is single-answer multiple choice, Part B is multiple-choice questions where more than one answer can be correct, and Part C includes short-answer and multiple true/false questions. You need to be a US citizen or green card holder to take this round.
Round 3: National Finals. The top 20 Semifinal scorers are invited to an in-person National Finals at Harvard University, run as part of Harvard's Pre-College Summer Science Program. Over roughly 12 days, you'll go through intensive instruction plus a theory exam and a lab-based practical exam. As of the 2027 cycle, National Finals is in-person only.
Round 4: International Biology Olympiad (IBO). The top 4 scorers from National Finals become Team USA and compete against 60+ countries at the IBO. The 2027 IBO will be held in Warsaw, Poland, from July 18 to 25, 2027.
When is the USABO? Key 2027 cycle dates
Stage | Date |
School registration opens | Already open (registration typically opens in August) |
Returning-school payment deadline | October 23, 2026 |
Final registration deadline (schools and students) | November 15, 2026 |
Open Exam | Expected late January-early February 2027 |
Semifinal Exam | Expected within weeks of the Open Exam results |
National Finals (Harvard University) | Summer 2027, exact dates not yet published |
International Biology Olympiad (Warsaw, Poland) | July 18-25, 2027 |
Dates shift slightly year to year, so always cross-check the official USABO calendar before you finalize your study plan.
What will you be tested on?
USABO content is organized around these focus areas:
Cell Biology
Animal Anatomy and Physiology
Plant Anatomy and Physiology
Ethology
Genetics and Evolution
Ecology
Biosystematics
Neurobiology
Bioinformatics
This is a wider net than most AP Biology curricula, which is exactly why students who've only taken AP Bio are often caught off guard by the Open Exam. Read our ultimate guide to AP classes here!
How to study for the USABO
You need a study plan that goes beyond your school's biology curriculum. Here's the reading list CEE and past competitors consistently point to:
Campbell Biology (latest edition) — the closest thing to a core USABO textbook.
Human Physiology by Sherwood
Essential Cell Biology by Alberts
Plant Biology by Raven
BioEd — free resource hub for life science educators
MacMillan Learning — over 100 tutorials on biology topics
Your school's AP or honors biology curriculum, as a baseline
Beyond textbooks, two things separate students who make Semifinals from students who don't:
Starting early. If your goal is the 2027 cycle, aim to be on a structured review schedule by October 2026, well before the Open Exam window opens.
Forming or joining a USABO club. CEE actively supports this through their Student Corner, and testing each other on weak topics is one of the highest-leverage things you can do with limited study time.
USABO practice tests and past exams
If you’re looking for more USABO resources, here's where to actually find real practice material:
Official past exams archive. CEE publishes Open and Semifinal exams with answer keys going back years. This is the single best practice resource available, and it's free.
Art of Problem Solving (AoPS). AoPS administers the USABO exams and runs the registration platform you'll use on exam day, so getting familiar with their interface ahead of time removes one source of exam-day friction.
Timed drills. Once you've worked through a few past Open Exams untimed, redo them under the actual 50-minute limit so you build pacing instincts, not just content knowledge.
Work through at least 3-4 years of past Open Exams before you sit the real one. The format has stayed fairly consistent year to year, so pattern recognition genuinely transfers.
Tips to help you score higher
Don't skip lab-based questions in your prep, even at the Open Exam stage. Practical reasoning shows up earlier than most students expect.
Focus your remaining time proportionally: if a focus area shows up more often in past exams, study it harder, don't split your hours evenly across all nine areas.
Review your school's AP Biology material first if you're short on time. It's a smaller lift than starting from Campbell cold, and it covers real overlap with USABO content.
If you're aiming for Semifinals or beyond, start timed practice at least 8-10 weeks out, not the week before.
Frequently asked questions
How difficult is the USABO? It's significantly harder than AP Biology, both in breadth (it covers topics like ethology and bioinformatics that most AP courses skip) and in depth. Roughly 12,000 students take the Open Exam each year, and only the top 10% advance to Semifinals, so difficulty scales fast after round one. If you want structured help building a biology research profile alongside Olympiad prep, Lumiere pairs students with PhD mentors for exactly that kind of support.
Who is eligible for the USABO? Any US student in grades 9-12 registered through a participating school, including homeschooled students who make arrangements in advance. The Open Exam itself doesn't require citizenship, though CEE's eligibility page currently states citizenship or a green card as a blanket requirement, so confirm with your school's coordinator if this affects you.
What's the score you need for the USABO? CEE doesn't publish a fixed passing score in advance. Recognition is based on percentile cutoffs: the top 20% of Open Exam scorers earn an Honorable Mention Certificate, and the top 30% earn a Certificate of Merit. Exact raw score thresholds shift every year depending on exam difficulty, so there's no single number to target.
Is the USABO or the USNCO harder? Both are genuinely difficult, and "harder" depends on whether biology or chemistry is your stronger subject. Structurally, they're similar: a high-volume open/local round, a steep cut to a small national group, then a study camp that produces a 4-person international team. If you're deciding between the two, read our USNCO prep guide and compare it against your actual coursework strengths rather than reputation alone.
When is the USABO open exam? For the 2027 cycle, it's expected in late January or early February 2027, though CEE hasn't published the exact date at the time of writing this blog. Registration closes well before that, on November 15, 2026.
How much does it cost to register for the USABO? Schools pay a $125 registration fee to activate their USABO account for the year. Homeschooled students arranging to test through a local school may be responsible for this fee themselves.
Does the USABO give scholarships or cash prizes? No. USABO doesn't offer scholarships or financial prizes at any round. The value is in the credential itself and the door it opens to the International Biology Olympiad, both of which carry real weight with selective college admissions offices.
What happens if I make USABO National Finals? You're invited to an in-person program at Harvard University, run as part of Harvard's Pre-College Summer Science Program, with roughly 12 days combining instruction and testing. The top 4 scorers there become Team USA and advance to the International Biology Olympiad.
Want to do research in biology before the USABO?
A strong USABO result is a great credential, but it works best as part of a broader research and academic profile, not a standalone bullet point. If you're building that profile out, check out our guides on biology research opportunities and other biology competitions worth considering.
If you want a research mentor to help you turn your biology interest into an independent research paper, Lumiere's Research Scholar Program pairs you 1-on-1 with a PhD mentor from Harvard, Oxford, and other top research institutions.
Stephen Turban is the co-founder of Lumiere Education and a graduate of Harvard College, where he earned an A.B. in Statistics before beginning a PhD at Harvard Business School. A former McKinsey & Company consultant and former researcher, his research has been covered by the Harvard Business Review, The Economist, BBC News, Freakonomics Radio, and the Washington Post. In his articles for Forbes, he writes on what students and professionals can learn from high school research, high school passion projects, critical thinking, and mentorship. At Lumiere, he leads a selective research program where students work one-on-one with a research mentor to develop an independent research paper. Connect with him on LinkedIn.