Premature infants are at high-risk of apnea after surgery. General anesthesia increases the risk of apnea. A 3-day-old male was scheduled for an anoplasty because of a low-type imperforated anus with a anoperineal fistula. The medical history was significant for premature birth at 345 weeks of gestation with a birth weight of 2,610 g. He had an irregular breathing pattern and self-limiting apnea. He also had bilateral 12th rib defect with substernal retraction. After an intravenous injection of ketamine 1 mg/kg and atropine 0.15 mg, a mask was positioned. A caudal block was performed via a 23 G angiocatheter using a single bolus dose of 0.8 ml/kg of 0.25% bupivacaine in the lateral position. He was immediately turned to a supine position and lithotomy position after slow injection of the drug. Anesthesia was maintained with isoflurane 0.2 0.6 vol.% in 50% O2 during preparation and operation under the masking. During 15 minutes of uneventful surgery, the infant remained comfortable but the breathing pattern was still irregular. No increase in the frequency of apnea was observed during the first postoperative day. A caudal block with light inhalational anesthesia was a successful method in a premature infant for anoplasty.