In 98 patients with cancer, the diagnostic value of measuring serum alkaline phosphatase, 5'-nucleotidase, γ-glutamyltransferase, and glutamate dehydrogenase activities were assessed as an aid to detection of liver metastases. All four enzymes showed diagnostic value, but 5'-nucleotidase appeared to have the greatest. It showed the lowest false-positive results (7.4%) with the highest predictive value of a positive test (85.7%) and agreement (81.3%). γ-Glutamyltransferase showed the lowest proportion of false-negative results (2.8%), but was the least specific (35% false-positive results). Analysis of various test combinations showed that the best agreement (77.5%) was obtained when the patients were divided into those who had no or only one abnormal test result, and those who had two or more abnormal test results. However, this was not better than the agreement for 5'-nucleotidase alone (81.3%). The agreement of 5'-nucleotidase and γ-glutamyltransferase (i.e., both tests were positive or negative) was excellent (91.4%), but such agreement included only 67% of the patients with liver metastases.