A study designed to assess smoking behaviour and attitudes towards smoking was undertaken in medical students of the Faculty of Medicine, University of Istanbul. A World Health Organization (WHO)-based multiple choice questionnaire prepared by the Tobacco and Health Committee of the International Union Against Tuberculosis and Lung Disease (IUATLD) was completed by 1,267 first- to final-year medical students in the Faculty of Medicine. Their mean(SD) age was 19.8(4.0) years. Non-smokers accounted for 74% of the students, 11.4% were smokers and 0.9% were heavy smokers. Daily smoking rate was 4.9% in the first year and 30.4% in the final year. In the first year, 75.5% of students and 91.5% of final-year students were aware of the fact that smoking is a cause of lung cancer, whereas 21.4% of first-year and 61.4% of final-year students gave correct answers to a question about the relationship between low birthweight and smoking. Attitudes were influenced by smoking with 78.6% of non-smokers and 64% of smokers saying that they would advise their patients against smoking. It appears that the study of medicine does not influence the behaviour of medical students against smoking, although it improves their knowledge of smoking-related diseases.