Thirty-six unpremedicated women due for gynaecological surgery were examined for time-dependent prolongation of the QT interval in the electrocardiogram (ECG) before and after induction of anaesthesia using either sevoflurane or propofol. The conventional inhalational technique to induce anaesthesia with sevoflurane. ECG recordings were taken before, 2, 5 and 10 min after drug administration. Sevoflurane significantly lengthened (P < 0.001) the heart rate corrected QT interval within 10 min from 434±5ms to 459±6ms (mean ±SEM). Already after 2 min of sevoflurane application a trend towards prolongation was visible. The critical value of 440ms in the rate-corrected QT interval was exceeded in four patients in the sevoflurane group (n=18) but in only in one patient in the propofol group (n=18). Rate-corrected QT interval prolongation caused by sevoflurane needs to be recognized early in order to prevent the critical ventricular tachycardia torsade de pointes