Abstract: Objective:To assess the efficacy of intravenous pretreatment with magnesium sulfate on propofol injection-induced pain.Methods:One hundred and sixty ASA Ⅰ -Ⅱ patients undergoing general anaesthesia were rando mly allocated into four groups:M,L,K and S group(forty in each group).A 20-gauge catheter was inserted into vein on the back of right hand for drug injection and anaesthesia,and with a rubber venous tourniquet 5 cm near wrist.In M,L,K and S group,patients were pretreated with i.v 20 mg /kg of magnesium sulfate(M),0.5 mg /kg of lidocaine (L),0.3 mg /kg of ketamine (K),and 5 ml normal saline (S),respectively.The occlusion was released after 1 min,2 mg /kg of propofol was injected into vein by the infusion at 0.5 ml /s.The incidence and intensity of pain was assessed by verbal rating scales (VRS).patients' MApand HR were recorded at the point of before administration,tourniquet released,after induction of anesthesia and endotracheal intubation.Results:The incidence of pain in M groupwas 25% compared to 55% for L group,50% for K groupand 95% for S group.The incidence and intensity of pain in all groups were significantly lower than in S group(P＜0.01).The incidence of pain in M groupwas significantly lower than in L group(P＜0.05),and was similar to K group; K groupwas similar to L group(P＞0.05).The intensity of pain in M groupwas significantly lower than in L,K and N group(P＜0.01),respectively,and there were no statistical differences in M,L and K group(P＞0.05).There were no significant differences in MApand HR between all groups.Conclusions:Combined with tourniquet technique,intravenous pretreatment with magnesium sulfate,lidocaine and ketamine are effective in attenuating propofol-induced pain.However,it has been observed that pretreatment with magnesium sulfate was the most effective.