The aim of the study was to assess sexual health knowledge of medical students. Participants from the student population of an English Medical School (University of Bristol) were asked to fill in a questionnaire on the Internet about sexual health issues. The number of correct responses to each question was analysed according to participants' gender and medical school year. While certain issues relating to sexually transmitted infections, contraception and confidentiality in HIV testing were well understood, there was poor knowledge about the failure rate of condoms, abortion rates and prevalence of chlamydia. Women knew more about the contraceptive pill than men. Although increased years of medical training had some benefit in improving the accuracy of knowledge, this effect was surprisingly small. Most medical students have inaccurate factual knowledge about certain important sexual health issues. We consider this to reflect poorly on sexual health awareness in young people in general. There is need for greater sexual health education for future doctors and for the general public.