One hundred and forty-one patients for general and urological surgery were anaesthetized by epidural anesthesia (PDA) using bupivacaine-CO2 0.5% solutions. A frequency peak for the initial dose between 21-23 ml was noted. The response time and latency period were found to be 2.99 +/- 1.40 min and 11.02 +/- 3.66 min (smallest time unit 0.5 min). The effective duration was 5.02 +/- 0.93 h. The sensory spread reached on average to T 6.06 +/- 1.41 segments for the patients with typical injection locations at L2/3-L4/5. A mean dose of 6.25 +/- 0.18 mg per spinal segment was used. Side effects were not seen apart from occasional hypotension. The failures were not related to the anesthetic drug. The degree of muscle relaxation was for the majority of cases evaluated at 2 +, which was sufficient for the abdominal operations. The results are compared with the data obtained using bupivacaine-HC1; the advantages of bupivacaine-CO2 are described.