The effectiveness of intravenous meperidine and warm local anesthetic for prevention of postanesthetic shivering was evaluated in urology patients undergoing epidural blockade for extracorporeal shockwave lithotripsy. When administered before the blockade, meperidine, 12.5 mg or 25 mg, was not significantly better than saline placebo for preventing postepidural shivering. Changes in the concentrations of catecholamines or lidocaine did not result in differences between patients who shivered and those who did not shiver. In a second experiment, patients receiving body-temperature or room-temperature epidural lidocaine did not differ with respect to the incidence of postanesthetic shivering, onset of sensory blockade, or core temperature during a 30-minute observation period. The authors concluded that neither meperidine, in doses employed, nor body-temperature lidocaine prevents shivering after epidural blockade. This shivering appears to be different from that observed during emergence from general anesthesia.