A survey on the smoking habits of medical students at the Arabian Gulf University has been carried out using an anonymous self-administered questionnaire. The response rate was 96.4% and a total of 91 male and 175 female medical students were included in the study. About 11% of the students of both sexes were smokers, 7% ex-smokers and 82% non-smokers. Among male students, 27.5% were smokers, 14.3% ex-smokers and 58.2% non-smokers. The corresponding percentages for their female counterparts were 2.3%, 3.4% and 94.3%, respectively. Fifty-eight per cent of the male smokers smoked ? 20 cigarettes/day, 29% smoked < 20 cigarettes/day and 13% were occasional smokers. Male medical students who lived with their parents or in the university residences were less likely to smoke than others who lived alone or shared an apartment with a friend. No significant association was found between students' smoking status and parental smoking. The survey has revealed that the prevalence of smoking among male medical students is relatively high and that the majority of smokers among the males started to smoke during their medical training, in contrast to elsewhere.