BACKGROUND: This study was designed to determine whether etomidate-based induction can provide better hemodynamics than a standard thiopental sodium-based anesthetic induction in elderly patients. METHODS: Sixty ASA physical status 1 or 2 elderly patients scheduled for elective surgery were randomly allocated into one of three groups (Group 1; thiopental sodium, Group 2; etomidate, Group 3; pre-treatment with 0.02 mg/kg of midazolam and etomidate). We measured and compared hemodynamic changes (mean arterial pressure, heart rate), the doses of thiopental sodium and etomidate for loss of consciousness, the incidence and grade of myoclonus, and the bispectral index during induction of anesthesia. RESULTS: There were no significant differences in mean arterial pressure and heart rate among the three groups. Myoclonus occurred in 45% of patients receiving etomidate, 40% of patients receiving midazolam pre-treatment and etomidate. Pre-treatment of midazolam reduced the dose of etomidate for loss of consciousness by 20% in Group 3. The values of BIS decreased significantly from 1 minute after infusion of thiopental and etomidate, and reached 56.9 +/- 12.3 in group 1, 41.8 +/- 9.1 in group 2, and 45.8 +/- 8.5 in group 3 just before endotracheal intubation. CONCLUSIONS: These results indicate that there is no significant difference between etomidate and thiopental sodium as anesthetic induction agents in elderly patients. Pre-treatment with a small dose of midazolam reduced the dose of etomidate for loss of consciousness, but did not affect the incidence of myoclonus and hemodynamic changes during induction of anesthesia with etomidate.