In a prospective study of drug overdose patients admitted to emergency rooms of 21 Toronto hospitals, 39% said they had taken a benzodiazepine. Benzodiazepines were used more frequently by females than males and by suburban than core hospital patients. Patients who overdosed on benzodiazepines were admitted to the hospital less frequently and arrived with less disturbance of consciousness than those who had used other drugs. Patterns of prescription in Ontario and patterns of overdose in Metropolitan Toronto were highly correlated.