Two routes to the IChO.

The American Chemical Society's three-part USNCO and the Royal Society of Chemistry's UK Olympiad — the two flagship pipelines that select for the International Chemistry Olympiad each summer.

2 competitions 1 archived 1 in audit

In This Department

Both papers.

U.S. National Chemistry Olympiad

Local 60-MC · National Parts I, II, III (incl. wet lab).

12 official PDFs normalized (Local + National 2022–2025). Calculator rules, supplied constants, embargo dates — all on file.

ACS · Local March →

Audit

Chemistry · Olympiad

UK Chemistry Olympiad

Round 1 written · Round 2 residential · IChO team.

Round 1 papers and mark schemes 2003–2025 publicly available on edu.rsc.org. Tens of thousands of students from 1000+ schools.

RSC · January →

An editor's note

Pick the one your timezone supports.

Both papers feed into the International Chemistry Olympiad. The USNCO route is gated to US-school students; the UK route is open to A-level students at the relevant year. For a student whose curriculum is neither, the cleaner choice is whichever paper they can sit at school.

The two papers reward different study habits. USNCO Local is dense and multiple-choice; USNCO National Part II is eight long problems; Part III is a real wet lab. UKChO Round 1 is a single 2-hour paper — closer in feel to BPhO Round 1 than to USNCO Local.

Past-paper coverage

USNCO: 12 papers (Local + National 2022–2025) fully normalized in the Tian2 archive. UKChO: 22 years (2003–2025) listed; archive in progress.

— The Editors