A prospective comparative study between liver enzymes, scintigraphy, ultrasonography and computed tomography for detection of liver metastases was performed in 113 patients who were eligible for operation for a carcinoma in the gastrointestinal tract. Twenty-three of the 113 patients (20 per cent) had liver metastases. The accuracy of scintigraphy was 79 per cent, of ultrasonography 85 per cent and of computed tomography 88 per cent. The results of these tests showed no statistical differences. Ultrasonography and computed tomography were significantly more accurate than alkaline phosphatase and gamma-glutamyl transpeptidase (respectively P less than 0.01 and P less than 0.05). Taking into account cost effectiveness, simplicity and patient tolerance, ultrasonography is the test of choice for the detection of liver metastases.