Background : Postoperative myalgia after administration of succinylcholine is a frequent complication after surgery. This study was designed to determine whether there was any association between postoperative myalgia and muscle relaxants. Methods : Sixty patients were assigned to three groups of equal size. Group 1, the patients received succinylcholine, 1.0 mg/kg for tracheal intubation. Group 2, received pancuronium 0.01 mg/kg, 4 minutes before administration of succinylcholine 1.5 mg/kg. Group 3, received pancuronium 0.01 mg/kg, 4 minutes before administration of pancuronium 0.09 mg/kg. Blood samples for determination of serum potassium concentration were taken before the induction of anesthesia and 3 minutes after tracheal intubation. The incidence and severity of muscle fasciculation and myalgia were assessed in a double-blind manner. Results : Serum potassium concentration was significantly increased in group 1. In group 2, incidence and severity of muscle fasciculation were significantly less than groups 1. Postoperative myalgia was significantly less in group 3 when compared with group 1 and 2. Conclusions : There was no significant correlation between succinylcholine induced fasciculation and postoperative myalgia. Pretreatment with pancuronium decreased the incidence of fasciculation and the changes of serum potassium concentration by succinylcholine, but has little effects on the succinylcholine induced postoperative myalgia. (Korean J Anesthesiol 1998; 34: 780∼785)