BACKGROUND: Even though propofol having many clinical merits, a vascular pain during intravenous administration of it could maKe us choose other induction agents. One of many METHODS to decrease vascular pain, the use of propofol preserved in a cold temperature (1 4degeesC) was introduced and Known to be effective. The purpose of this study was to compare vascular pain of cold propofol with that of thiopental as induction agents. METHODS: Sixty adult patients for elective surgery were randomly assigned to the two groups according to receiving thiopental (Group I, n = 30) or propofol (Group II, n = 30), then they were divided randomly into two subgroups according to the selection of vascular size; vein on the dorsum of hand or antecubital fossa. As an induction agent, 2.5% thiopental (5 mg/Kg) or cold 1% propofol (2 mg/Kg) were given intravenously during 40 sec. The severity of vascular pain (classified by 4 points verbal category system) and the incidences of pain were compared according to the induction agents and the selection of vascular size. The incidences of moderate to severe pain according to the selection of induction agents were compared. RESULTS: There was no significant difference in the severity, incidence of pain or incidence of moderate to severe pain in both groups, There was no significant difference in the incidence of pain according to the vascular size. CONCLUSIONS: As cold propofol was given slowly (during 40 sec), the vascular pain was not significant to hinder the selection of propofol as an induction agent compared with that of thiopental.