OBJECTIVE: To determine whether doctors who abuse substances differ from controls in terms of their physical and psychological well-being, and their marital and occupational functioning. DESIGN AND PARTICIPANTS: The 44 doctors concerned in all cases of substance abuse which came before the Medical Board of Victoria between 1984 and 1990 were invited to complete a demographic questionnaire, psychological tests and a semi-structured interview. A control group of 42 doctors, obtained from the Medical Register, was also invited, and the groups were compared. SETTING: The study was carried out at St Vincent's Hospital, Melbourne, under the auspices of the Medical Board of Victoria. RESULTS: Questionnaires were returned by 70% of the drug-dependent doctors and 83% of the controls. However, interviews were given by only 20% of the drug-dependent doctors. The groups differed significantly in terms of marital status (P < 0.002), overall health (P < 0.003), general wellbeing (P < 0.0009), and having experienced physical illness (P < 0.02) and psychiatric illness (P < 0.006) since graduation. No differences were found on the standardised questionnaires; this may reflect successful treatment. CONCLUSION: Substance abuse in medical practitioners is a major problem and is associated with considerable morbidity. Prevention and early intervention are crucial.