BACKGROUND: caudal anesthesia is a safe and reliable technique for surgical anesthesia as well as an alternative to narcotics for postoperative analgesia for procedure below umbilicus. Onset time and duration of local anesthetics had been influenced by local anesthetics with combined drugs. We wanted that the time required for the onset of local anesthesia should be short and long enough to allow time for the contemplated surgery. METHOD: To investigated the effect of lidocaine with combined drugs, 120 ASA physical status I, II patients who underwent perianal surgery with caudal anethesia. The patients were diveded into 5 groups : control group received 1.5% lidocaine 27ml, group I received lidocaine with epinephrine (1:200,000), group II received lidocaine with morphine 2mg, group III received lidocaine with fentanyl 50 g, group IV received lidocaine with clonidine 75 g. We have compared the onset time and duration of analgesia of 5 groups. RESULTS: 1. The onset time of analgesia for pin prick test were not significantly changes between groups. 2. The duration of analgesia was significantly more prolonged in group II(863.8 222.1 min) than other three group I, III, IV. 3. The most common side effect was urinary retention(20 cases, 16.7%) in all groups(n=120). 6 cases(24%) in group II(n=25), 2 cases(8%) in group III(n=25) were complained of pruritus. Bradycardia and hypotension were observed in group IV(n=20) (each 1 cases, 5%). CONCLUSIONS: It is suggested from the above results that the morhine group during caudal anesthesia can produce more prolonged duration of analgesia.