OBJECTIVE: To estimate the prevalence of smoking habits among male medical students at the College of Medicine, King Saud University, Riyadh, Kingdom of Saudi Arabia (KSA). METHODS: We carried out this cross-sectional study using Arabic questionnaires distributed to the medical students in the College of Medicine, King Saud University, Riyadh, KSA at different educational levels from September 13 to September 25, 2005. A total of 322 medical students completed the questionnaires (response rate 80.5%). RESULTS: The study shows that 13% of male medical students were currently active smokers, 5.3% were ex-smokers, and 38.2% were passive smokers. The types of smoking included sheesha 44.1%, cigarette 32.2%, and both 23.7%. The common reason given for the smoking behavior was the influence of friends (35.6%). The study shows that 57.1% of current smokers were motivated to stop smoking. CONCLUSION: There is an urgent need to promote multi-disciplinary health education activities at different age groups in order to prevent young age students from smoking, and to help smokers to quit