Past papers are the single highest-value resource for USABO Open and Semifinal preparation. The format, pacing, and characteristic question style are remarkably consistent year-on-year. Solve every available paper at least once — twice for the best diagnostic value.
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We share past papers with worked solutions to enrolled USABO programme students. To respect CEE's distribution norms, individual papers are sent on request via WhatsApp rather than hosted publicly here. Reply "past papers" in the chat and we'll send the year you're asking for within an hour.
Last updated 14 October 2026, checked against the organiser's official pages.
Sources: USABO 2027 calendar (CEE) · About the exams (CEE) · Guidelines and eligibility (CEE)
Listed newest first. Each year includes both the Open Exam paper and the corresponding Semifinal paper, plus our worked solutions and topic tagging. Year-specific notes below are summary characterisations from Cerebrum faculty review — not authoritative answer keys.
| Year | Open Exam | Semifinal | Notes |
|---|---|---|---|
| 2024 | Request via WhatsApp | Request via WhatsApp | Open emphasized molecular signaling and population genetics. Semifinal had a notable phylogenetics section. |
| 2023 | Request via WhatsApp | Request via WhatsApp | Biostatistics-heavy year. Strong emphasis on data interpretation in both Open and Semifinal. |
| 2022 | Request via WhatsApp | Request via WhatsApp | Return to full normal Semifinal format after pandemic adjustments. |
| 2021 | Request via WhatsApp | Request via WhatsApp | Pandemic-era format adjustments. Useful for understanding USABO question style. |
| 2020 | Request via WhatsApp | Request via WhatsApp | Open paper administered before pandemic disruption; Semifinal was modified. |
| 2019 | Request via WhatsApp | Request via WhatsApp | Strong cell-biology and physiology emphasis. |
| 2018 | Request via WhatsApp | Request via WhatsApp | Heavy ethology questions — useful calibration for AP Biology students. |
| 2017 | Request via WhatsApp | Request via WhatsApp | Classic format. Good first paper to attempt cold. |
| 2016 | Request via WhatsApp | Request via WhatsApp | Solid all-rounder paper. Useful baseline diagnostic. |
| 2015 | Request via WhatsApp | Request via WhatsApp | Earlier-format Open Exam. Useful for understanding how USABO has evolved. |
The students who clear USABO are the ones who treat past papers as a study technique, not just a content drill. Here's how the strongest performers we coach do it.
Pick the oldest paper in your archive (2017–2018) and sit it cold under exam conditions — 50 minutes, no books, no internet. Score it honestly. This is your baseline.
Maintain a spreadsheet: column A is the question stem, column B is the topic (Cell Bio, Genetics, Plant Phys, Ethology, etc.), column C is right/wrong. After 3–4 papers, you'll see your weakest 2 topics. That's your study target.
Solving each paper twice (a week apart) is more useful than rushing through 10 papers once. The second sit teaches you which mistakes were knowledge gaps vs reading-the-question errors.
Don't exhaust the archive. Keep your two newest papers (e.g. 2023, 2024) sealed until the final week before USABO Open. Sit them under full exam conditions as your dress rehearsal.
Enrolled USABO programme students get all 10 years of papers, our worked solutions with topic tagging, and weekly office hours to discuss tricky questions.
Tell us which years you need. We will email the papers with worked solutions and a short note on what each one tested.
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