Objective: To investigate alcohol and illicit drug use in a cohort of dental undergraduates through to VT year. Setting: A UK dental school (with a medical school comparison group). Subjects and methods: A cohort of dental students anonymously completed a lifestyle questionnaire about drinking and smoking, illicit drug use, stress, anxiety and depression in the spring of 1995 and 1998 as second and final year undergraduate students respectively, and in the summer of 1999 after one year working as qualified dentists. A parallel cohort of medical students also anonymously completed the questionnaire at the same time points in their undergraduate course as for the dental students, and at the end of a year working as Pre-Registration House Officers (PRHOs). Results: The proportion of dental students in Newcastle drinking above the recommended low risk lim its of alcohol declined from 47% as second year students to 25% as final year students and then it increased to 41% as qualified dentists, whilst in medical students it steadily increased over the three time points of the survey (33% to 43% to 54%) A greater proportion of dental students were drinking at hazardous levels at all three time-points, compared with medical students. Experimentation with illicit drugs ranged from 47% as second year students to 54% as final year students and to 51% as dentists The prevalence of illicit drug use in medical students was similar to that in dental students. Forty seven per cent of the dental student cohort as second year students, 67% as final year students and 16% as dentists suffered from possible pathological anxiety, compared with 47%, 26% and 30% in the medical student cohort. The proportion of dentists suffering from stress decreased from 72% as final year students to 19% as dentists. In the medical student group, the proportion increased from 32% as final year students to 39% as PRHOs. Conclusion: This longitudinal study revealed that a high proportion of dental students from Newcastle continue to drink excessively and experiment with illicit drugs both as undergraduates and as practising dentists. A significant proportion also suffer from anxiety and stress. Further measures are needed in order to reduce alcohol and substance misuse and stress and anxiety among dental students and dentists.