Observations by health-care professionals suggest that the use of anabolic androgenic steroids (AAS) may be associated with lethal complications, but this has not yet been confirmed by controlled epidemiological studies. Here, we investigated the diagnoses (in the Swedish patient care records) and mortality rate among patients who tested positively for the presence of AAS (n = 248) in connection with receiving medical care. Patients who had tested negatively (n = 1215) were used for comparison. The proportions of patients who had received institutionalized care for substance abuse, psychiatric disorder or central thoracic pain were significantly higher in the AAS-positive subjects (RR = 2.2, 95% CI = 1.2-4.2; RR = 2.1, 95% CI = 1.4-3.2 and RR = 3.5, 95% CI = 1.1-10.9, respectively). Furthermore, unspecified convulsions were highly over-represented in the AAS-positive group (RR = 53.9, 95% CI = 7.0-415.7) and one of these patients died during a seizure. The standardized mortality ratios (SMR) in the AAS-positive patients and -negative patients were 20.43 (95% CI = 10.56-35.70) and 6.02 (95% CI = 3.77-9.12), respectively. The relatively higher SMR in the AAS-positive patients was observed irrespective of what type clinic had referred the patients for AAS testing. In conclusion, use of AAS appears to be an indicator of increased risk for premature death in several categories of patients. However, the nature of the association between AAS and premature death remains unclear and additional research on this question is urgently required.