Preoperative biochemical liver function tests and computerized axial tomographic (CAT) scans were performed on 100 patients as part of a prospective randomized study of treatments for liver metastases from colorectal cancer. The CAT scans reliably reflected the presence of disease in most patients but only accurately demonstrated the number and location of metastases in 43% of the patients. Extrahepatic metastases were present in 35 patients but were only seen on the CAT scans in three of these patients. The biochemical tests, which were useful for detecting hepatic metastases, were alkaline phosphatase (AP), lactic dehydrogenase (LDH), and carcinoembryonic antigen (CEA). When hepatic desease was minimal, these tests were less likely to be elevated than when there was extensive disease. Even with the combination of late generation CAT scans and biochemical tests, the accurate quantification and location of hepatic metastases and extrahepatic disease require a surgical assessment.