BACKGROUND: Propofol often causes pain when injected into small peripheral veins, but the pain can be minimized by using a larger vein. This study was designed to determine whether local warming of the injection site and forearm before propofol injection is effective in reducing pain. METHODS: Sixty adult patients undergoing general anesthesia for an elective surgery were randomly allocated to one of two groups. All were unpremedicated and had an 18-gauge cannula inserted into a cephalic vein on the wrist. Patients in group 1 (n = 30) received 1% propofol at room temperature. Patients in group 2 (n = 30) received 1% propofol after local warming (36-37 degrees C) of the injection site and forearm using a forced-air warming system (Bair Hugger(R)). For each patient, the pain during injection of the propofol solution was graded as none, mild, moderate, or severe. RESULTS: Overall the incidence of pain was significantly reduced in group 2 (36.7%) compared with group 1 (66.7%). No patients complained of pain at the injection site and forearm in group 2. However, there was no significant difference in the incidence or severity of pain on the elbow and axilla between the two groups. CONCLUSIONS: We found that local warming applied to the injection site (wrist) and forearm before propofol injection is significantly effective in reducing pain at the injection site and forearm, but there was no improvement of pain on the elbow and axilla when injecting.