During a 5-month period, 18 (8%) of 212 patients admitted to a psychiatric unit affiliated to a teaching hospital were found to have a catatonic syndrome associated with various nonorganic mental disorders. Signs and symptoms of motor retardation predominated the clinical presentations. In the course of a prospective, open study, all 18 patients were challenged by a small dose of oral lorazepam or intramuscular diazepam. Catatonic signs and symptoms in 2 patients showed an immediate, complete, and sustained response to the medication. The remaining 16 patients were maintained on 1 of the 2 benzodiazepines for the next 48 h when their motor status was re-evaluated. Significant clinical improvement was detected in all but 2 patients. However, 9 patients needed electroconvulsive treatment to achieve further improvement. Short-term benzodiazepine administration proved to be a safe and effective treatment of the catatonic syndrome.