OBJECTIVE: To assess if use of psychotropic drugs is associated with an increased risk of admission for heat-related pathologies during a heat wave period. METHOD: We conducted a matched case-control study. Cases were defined as subjects admitted to an emergency department for heat-related pathology (hyperthermia or heat stroke) over the August 2003 heat wave. Controls were defined as subjects living in the same area but not hospitalised over the same period and who had at least one prescription form submitted for refunding by the social security insurance in July 2003. Multivariate analyses were used to identify psychotropic drugs independently associated with hospital referral during the heat wave period. RESULTS: Out of the 1405 patients admitted to the emergency department, 56 (4%) presented with heat-related pathology. The mean age of cases was 83 years. Multivariate analyses showed that cases were more likely than controls to be treated with anticholinergic drugs (OR 6.0, 95% CI 1.8-19.6), antipsychotics (OR 4.6, 95% CI 1.9-11.2) or anxiolytics (OR 2.4, 95% CI 1.3-4.4). CONCLUSION: In special risk situations such as heat waves, the risk/benefit ratio of psychotropic drugs which could interfere with body temperature regulation has to be carefully assessed, particularly in the elderly.