Fifteen patients undergoing total hip and total knee replacement were studied prospectively to evaluate postoperative pain relief provided by an epidural infusion of fentanyl citrate, with and without lidocaine hydrochloride, and changes in arterial flow to the lower extremities. The patients were randomly placed in three groups: group 1 received epidural fentanyl, 5 micrograms/mL; group 2 received epidural fentanyl, 5 micrograms/mL with 0.75% solution of lidocaine; and group 3 received epidural fentanyl, 5 micrograms/mL with 1.0% solution of lidocaine. All patients received 1.5% solution of epidural etidocaine hydrochloride with epinephrine 1:200,000 for intraoperative anesthesia. No clinical evidence of deep vein thrombosis, tachyphylactic reaction to lidocaine, orthostatic hypotension, or motor block was demonstrated in any patient. The addition of lidocaine to the epidural fentanyl infusion did not improve pain relief or allow a decrease in the rate of infusion. Patients in all groups had improved arterial flow to the lower extremities 24 hours postoperatively.