To assess the effect of ethnicity and gender on medical student examination performance. Cohort study of Year 3 medical students in 2002 and 2003. Royal Free and University College Medical School, Imperial College School of Medicine. A total of 1216 Year 3 medical students, of whom 528 were male and 688 female, and 737 were white European and 479 Asian. Performance in summative written and objective structured clinical examinations (OSCEs) in July 2002 and 2003. White females performed best in all OSCEs and in 3 out of 4 written examinations. Mean scores for each OSCE and 2 out of 4 written examinations were higher for white students than for Asian students. The overall size of the effect is relatively small, being around 1-2%. Students of Asian origin, of both genders, educated in the UK, using English as their first language, continue to perform less well in OSCEs and written assessments than their white European peers.