BACKGROUND: We have used thiopental sodium as an induction agent traditionally, but a recently introduced induction agent, propofol, is gaining popularity among anesthesiologists. The purpose of this study was to compare the difference in induction time by measuring the hypnotic time. METHODS: Sixty adult patients (ASA class I or II) scheduled for elective surgery under general anesthesia were randomly assigned to receive 5 mg/kg of thiopental (Group I) or 2 mg/kg of propofol (Group II), respectively, as an induction agent. The induction time by using Eyelash reflex (from the start of administration of induction agent to the time of reflex loss) was measured after the administration of thiopental and propofol and compared between these two groups. RESULTS: The induction time using ER in Group II (52.2 +/- 12.0 s) was not significantly longer than Group I (50.4 +/-9.4 s). CONCLUSIONS: We concluded that propofol had the same induction time as thiopental for induction of general anesthesia.