Computed tomography, ultrasound, nuclear scintigraphy, and laboratory tests (lactic dehydrogenase, alkaline phosphatase, and 5-nucleotidase) were compared in 135 patients with gastro-intestinal carcinoma to define the most useful test to detect hepatic metastases. Thirty-six patients (26.7 per cent) had hepatic metastases at laparotomy. Sensitivities were low: 46.2 per cent for nuclear scintigraphy, 57.6 per cent for ultrasound, 67.7 per cent for computed tomography and 62.9 per cent for lactic dehydrogenase. Accuracies ranged from 62.9 (lactic dehydrogenase) to 77.6 per cent (nuclear scintigraphy). No significant differences were found. Accurate and efficient detection of hepatic metastases is hampered by relatively low sensitivity, specificity and accuracy of the conventional imaging tests and laboratory tests.