This study was designed to evaluate the effect of target controlled infusion of propofol on QTc interval and tracheal intubation. Twenty-five unpremedicated, ASA class I or II patients were selected and target concentration infusion of propofol at 5 microg x ml(-1) was used throughout the study. The QTc interval was measured before anaesthetic induction (baseline, T1), 10 min after propofol infusion (T2), immediately after tracheal intubation (T3), and 1 min after tracheal intubation (T4). The QTc interval increased significantly at 10 min after the propofol infusion started compared to baseline (p = 0.003). After tracheal intubation, the QTc interval was further increased when compared to that at T2 (p < 0.0001). The increased QTc interval was within normal limit and no patient had an arrhythmia. In conclusion, although statistically significant, the increase in QTc interval was too small to be clinically significant during propofol infusion. However, the combination of propofol and tracheal intubation must be used carefully in patients with prolonged QTc interval.