BACKGROUND: The purpose of this study was to assess the changes in serum potassium and creatine kinase concentrations and the incidence of fasciculations and myalgia when rocuronium and lidocaine were used in combination and separately as pretreatment before succinylcholine. METHODS: We studied 60 patients undergoing a minor elective surgery, in a prospective double blinded method. Three groups each with 20 patients were pretreated before a 1.5 mg/kg succinylcholine administration with 0.05 mg/kg rocuronium three min before (group R), 1.5 mg/kg lidocaine 30 sec before (group L), or both rocuronium and lidocaine (group RL). Serum potassium and creatine kinase were respectively measured 5 min after succinylcholine administration and 24 h after the operation. Fasciculations and myalgia on postoperative day 1 and day 2 were evaluated. RESULTS: The increase in creatine kinase and incidence of myalgia on postoperative day 1 was less in the RL group than in the R group and L group. The incidence of fasciculations was higher in the L group than in the R group and RL group. There was no increase in serum potassium in any group. CONCLUSIONS: The combined use of rocuronium and lidocaine was more effective in reducing creatine kinase and postoperative myalgia than when they were used separately. However, the fasciculations were only reduced by the use of rocuronium.