Liver metastases from colorectal carcinomas occur frequently. While surgical resection offers the only hope for long-term cure, unsuspected bilobar metastases or extrahepatic metastatic disease may be found at laparotomy, precluding hepatic resection for cure. In this setting intraoperative interstitial hepatic irradiation using the Gamma Med II (Mick Radio-Nuclear Instruments, Bronx, New York) remote afterloading irradiator and an Iridium-192 source permits delivery of a tumoricidal dose to liver tumor(s) with a limited radiation dose to adjacent normal liver. Six patients underwent laparotomy for potential resection of hepatic metastases in a shielded operating room equipped with remote anesthesia monitoring capability and were found to be unresectable. An upper hand retractor facilitated liver exposure during the exploratory and subsequent radiation phases of the procedure. Intraoperative interstitial radiation therapy was performed in each patient. No significant complications occurred on follow-up from 2 to 9 months. Hepatic tumor regression or stabilization occurred on sonography and/or CT scan in each case with a median follow-up of 5 months. The technique offers the potential to ablate discrete tumor nodules within the liver. Ongoing clinical trials will determine the role of intraoperative interstitial radiation in the treatment of hepatic metastases.