The effects of continuous intravenous infusion of lidocaine on postoperative paralytic ileus in cholecystectomized patients was investigated in this double-blind study. An infusion of lidocaine (3 mg/min, n = 15) or an infusion of an equal volume of saline (n = 15) was started 30 min before induction of anesthesia and continued for 24 h after surgery. Postoperative colonic motility was evaluated by radiopaque markers and serial abdominal radiographs. A record was kept of the first passage of gas and feces. Results showed significantly earlier return of propulsive motility in the colon of lidocaine-treated patients. Radiopaque markers in the lidocaine group were propelled significantly earlier from the cecum/ascending colon to the transverse colon (P less than 0.05) and appeared significantly earlier in the descending colon (P less than 0.05) and the rectosigmoid colon (P less than 0.05) than in saline-treated patients. Despite the fact that the mean time for postoperative defecation occurred 17 h earlier in lidocaine-treated patients, differences between the groups were not statistically significant--a fact due, perhaps, to great individual variations in defecation habits. The time to first passage of gas, a variable representative of changes in anorectal or colonic tone rather than propagative motility, also did not differ significantly between the groups. No adverse reactions to lidocaine were reported. The results suggest that continuous intravenous infusion of lidocaine during the first postoperative day shortens the duration of paralytic ileus in the colon after abdominal surgery. Suppression of inhibitory gastrointestinal reflexes by reduction of postoperative peritoneal irritation is suggested as the mechanism of action.