Background: The incidence of pain on injection of propofol varies between 30 and 100%. A variety of pretreatments have been tried to alleviate this problem such as a local anesthetics, cooling and opioids. However, none of these pharmacological maneuvers were satisfactory yet. In a recent study, subhypnotic doses of both thiopental sodium and propofol decrease the acute pain. We report a comparison of thiopental sodium, lidocaine and placebo on the incidence and severity of pain on injection of propofol. Method: A controlled, double-blind study was performed to compare the prior administration of intravenous saline 2 ml(n=30, group S), lidocaine 20 mg(n=30, group L) and thiopental sodium 50 mg(n=30, group T) in alleviating the pain by propofol. Injection pain was assessed with the four-point verbal categorical scoring system. Result: The incidence of injection pain during induction was lower in group L(30%) and T(17%) than group S(77%). The incidence of injection pain was lower in group T(17%) than group L(30%), but not significant statistically. The pain scores for recall of pain in the recovery room was simlar to those pain during propofol induction. Conclusion: The pretreatment of thiopental sodium can be effective in reducing both incidence and severity of propofol injection pain and has similar effect to lidocaine to prevent propofol injection pain.