Epidural anesthesia is widely practiced for lower aMominal surgery and painless delivery in many hospitals and its complications are much lower than that of spinal anesthesia, Lidocaine is a most commonly using local anesthetic in clinics and it has been used exten-sively for epidural anesthesia with very good results. It has a rapid onset of acton with a good analgesic effect and a reasonable duration of action (about l - 11/2 hr). The primary purpose of this study is to observe toxic levels of plasma lidocaine concentration in patients who receive different doses of lidocaine epidurally. Twenty-two adult patients were divided into three groups. With patients in a sittng position, single epidural anesthesias were perfomed with a 17 gauge Tuohy needle. The 2% lidocaine mixed with 1: 200,000 epinephrine was used as a local anes- thetic. Of these, 7 patients in group l were given 400 mg and 8 patients in group 2 were given 500 mg and 7 patients in group 3 were given 600 mg. The plasma concentrations of lidocaine were measured by immunofluorescence assay at the intervals of 5, 10, 15, 30, 45 and 60 minutes. The peak plasma concentrations in the group 1, 2 and 3 were 2.24±0.51, 3.84±0.90 and 4.36±1. 16ug/ml (mean±SD) respectively. The peak plasma concentrations were measured 15 and 30 minutes after the epidural injection in group 1, 2 and 3 respectively. The maximum peak plasma concentration among 22 patients was 6.48ug/ml. These results indicate that the injection of 2% lidoeaine 500, 600mg with epinephrine is considered dangerous to some extent because the plasma concentrations of lidocaine exceed toxic levels occasionally.