OBJECTIVE: To assess the behaviour, knowledge and attitudes towards smoking among medical students in Sousse, TunisiDESIGN: A cross-sectional survey in classroom settings using a self-administered questionnaire was conducted at the School of Medicine during September 2004. RESULTS: The numbers of students who entered the first and the fifth years of medical training at the University of Sousse in 2004 and completed the questionnaire were respectively 120 and 110. The population age ranged from 18 to 21 years (mean 19 +/- 0.62 years) in first year students and from 22 to 30 years (mean 23 +/- 1.38 years) in fifth year students. The prevalence of daily smoking (both sexes combined) was 4.5% among first year students and 16.7% among final year students. The prevalence of daily smoking according to sex was 29.6% among boys and 0.7% among girls. Over 90% of students thought smoking was harmful to health, but there was considerable underestimation of its causal role in a number of diseases, notably coronary heart disease, bladder cancer and peripheral vascular disease. There were important defects in both knowledge and motivation regarding counselling patients to stop smoking. CONCLUSIONS: The results of this study may provide baseline data to develop an anti-smoking programme in the university.