As part of a program of postmarketing surveillance, the use of flumazenil was monitored prospectively in a New Zealand public hospital for a period of twelve months. A questionnaire on usage, efficacy and side-effects was completed by clinicians for 118 patients receiving the drug. Our conclusions are these: 1. Flumazenil was used most frequently after anaesthesia and in the initial management of intentional drug overdose. 2. In two-thirds of cases, flumazenil was used to antagonise benzodiazepines in the presence of non-benzodiazepine drugs and its efficacy was primarily determined by the presence of these latter drugs. 3. The complications of flumazenil are mild although important complications may arise from interaction with other drugs and unmasking of conditions such as postoperative pain. 4. Resedation was common (24%), although rarely a problem unless large doses of benzodiazepine agonist had been administered or if other hypnosedatives were given subsequently.