Questionnaire surveys of medical students in an Irish university were carried out in 1973 (n=765), 1990 (n=522) and 2002 (n=537), with differentiation of western students (e.g., from the Republic of Ireland, the UK, or Australia) and non-western students (e.g., Malaysia). We report on changes in tobacco smoking, drinking and drug-taking over three decades, and we note that, among western students, estimated prevalence of being a current smoker has declined overall from 28.8% in 1973 to 15.3% in 1990 to 9.2% in 2002 (p<0.001), falling in both males (p<0.001) and females (p<0.01). Ex-smokers rose from 5.9% to 15.1% between 1990 and 2002, corresponding with the decline in current smokers. The prevalence of current drinkers has risen over the period, to 82.5% among western students in 2002 (p<0.05); female drinking has increased steadily since 1973 (p<0.001), and the overall proportion of CAGE-positive drinkers has risen since 1990 (p<0.001). The mean weekly alcohol consumption has risen in both sexes since 1990 (males 14.3 units to 19.4, p<0.01; females 6.0 to 9.5, p<0.001). There was an increase in the proportion of students ever offered drugs between 1973 and 2002 (p<0.001). Although smoking rates have fallen, our findings show a marked increase in alcohol and drug consumption between 1973 and 2002. Personal misuse of addictive substances by doctors may mean that doctors will fail to take misuse by patients seriously. A need for preventative and ameliorative action during the medical school years is clear.