Abstract In a clinical study involving 16 surgical patients receiving epidural hydromorphone for postoperative analgesia, we compared the use of a continuous infusion technique to an intermittent bolus technique (involving the use of a PCA device). Although comparable analgesia was achieved in the 2 treatment groups during the 48 h study period, the hydromorphone usage (mean value ± S.D.) was significantly higher in the continuous infusion group (10.2 ± 3.6 mg vs. 4.6 ± 2.2 mg in the intermittent bolus group). In spite of this difference in the analgesic dosage requirement, the side effect profile was similar for the 2 groups. Further studies are needed to confirm this observation and to determine the implications with respect to postoperative recovery.