This study was to investigate the transfer of cefmenoxime (CMX) to the retroperitoneal fluid after extensive panhysterectomy. Twenty-two cases were examined and they were divided into 2 groups, 10 with 1.0 g and 12 with 2.0 g bolus intravenous administration of CMX. In 1.0 g group, CMX concentration in the retroperitoneal fluid was observed 42.0 +/- 9.59 micrograms/ml (Mean +/- S.D.) at 1 hour and thereafter decreased gradually, but it still remained 7.91 +/- 5.18 micrograms/ml at 6 hours after the administration. In 2.0 g group, its concentration was 33.4 +/- 34.5 micrograms/ml at 30 minutes and reached to the peak level of 45.1 +/- 24.6 micrograms/ml at 1 hour and then declined slowly, but it remained 13.3 +/- 8.28 micrograms/ml at 6 hours after the injection. The results demonstrated sufficient transfer of CMX to the retroperitoneal fluid.