In order to firstly evaluate the efficacy of flumazenil in reversing benzodiazepine-induced sedation because of drug overdose and secondly to register adverse events, 13 patients admitted to the intensive care unit because of drug intoxication, were given flumazenil intravenously to a maximum of 1.0 mg. Sedation state was scored on a modified Glasgow Coma Scale and arterial blood pressure, heart rate and arterial blood gases were recorded before and after flumazenil was given, and every 30 min for 2 h. Results showed that flumazenil reversed the sedation due to benzodiazepines effectively increasing the coma score significantly (P less than 0.005). We found no change in arterial blood pressure (apart from one patient), heart rate or arterial blood gases. Two patients gave further information about drug intake after flumazenil was given. Six patients became resedated, only one needed additional flumazenil. One patient developed a hypertensive crisis after flumazenil was given as a result of the unmasking of an untreated hypertension. Another patient aspirated gastric content to the trachea during resedation and needed respiratory support.