BACKGROUND: The clinical efficacy of electroconvulsive therapy (ECT) primarily depends on the adequacy of the seizure duration, but the intravenous anesthetics which are commonly used for ECT may possess anticonvulsant properties and shorten the seizure duration. The aim of this study was to compare the effects of propofol and etomidate on seizure duration and hemodynamic responses during ECT. METHODS: 30 patients undergoing maintenance ECTs were evaluated and divided into two groups randomly. Hypnosis was induced with a bolus injection of either 1.5 mg/kg of propofol or 0.3 mg/kg of etomidate in each group. Time to unconsciousness, seizure duration, heart rate, mean arterial pressure and recovery time were measured after delivery of electrical stimulus. The dynamic energy (joules) delivered was recorded. Correlation between seizure duration and recovery time was calculated and the rates of seizure induction failure after first electrical stimulus were compared. RESULTS: The seizure duration was shorter in the propofol group (34.0 +/- 3.8 s) than in the etomidate group (50.0 +/- 4.0 s)(P < 0.01). The heart rate was significantly lower in the propofol group (132.1 +/- 3.8, 99.7 +/- 6.2 bpm) than in the etomidate group (146.0 +/- 4.2, 119.8 +/- 7.5 bpm) at the time of ECT and 1 min after ECT respectively (P < 0.05). The mean arterial pressure was significantly lower in the propofol group than in the etomidate group from the time of ECT to 10 min after ECT (P < 0.05). CONCLUSIONS: Propofol showed excellent hemodynamic stability and was a good hypnotic for ECT therapy, but etomidate might be a useful alternative to propofol in patients who have an inadequate seizure duration.