A questionnaire to elicit information about smoking habits and knowledge of the risks of smoking was administered to 100 students (53 men and 47 women) in the graduating class of 1993 at the Cerrahpaşa Medical School of Istanbul. Forty-three percent of the men and 27% of the women students were smokers. All but one of the 100 students were aware that smoking is a risk factor for both lung and laryngeal cancers, and 44% of the smokers believed that cessation of smoking by the smoking population could decrease the incidence of lung cancers to less than half of its present level. These data suggest that awareness of the risks of smoking is not enough to motivate smokers to quit, even when they are young physicians. Of the nonsmokers, 87.5% indicated that they would attempt to restrain their younger siblings from smoking, whereas the corresponding figure for smokers was 58.3%. The smokers and the nonsmokers answered two of the questions on the questionnaire significantly differently. Thirty-six percent of the mothers of the nonsmokers and 31% of their siblings were also smokers, whereas the corresponding figures for the nonsmokers were 18% and 13% (half of the fathers in both groups smoked). Thus, family and the environment appear to influence smoking behavior. Successful modification of smoking habits will necessitate more education of the general public.