Rational : Minimizing the pain from propofol injection is clinically important because it may influence patient's perception regarding the quality and acceptability of general anesthesia. Objective : To compare the perception of pain after a pretreatment dose of 1.0 vs 1.5 mg/kg of thiopentone prior to induction of general anesthesia with propofol. Materials and Methods : We included 274 non-premedicated, ASA class I or II patients scheduling for elective surgery in a randomized, double-blind trial. Patients were allocated into two groups : Group T 1.0 was pretreated with an injection of 4-ml of solution with 1.0 mg/kg of thiopentone and Group T 1.5 was pretreated with 1.5 mg/kg of thiopentone. We used a verbal rating scale to assess patient's injection pain while administering propofol. Results : The incidence of injection pain was 48% and 47% in Groups T 1.0 and T 1.5 respectively. The severity of pain experiencing mild, moderate and severe degree was similar in both groups : 34% vs 32%, 10% vs 10% and 2.9% vs 3.6% of patients in Groups T 1.0 and T 1.5 respectively. Conclusion : Thiopentone pretreatment reduced propofol injection pain in half of our patients ; there was, how ever, no significant difference between using 1.0 vs 1.5 mg/kg.