The objectives were to compare the role of CT during arterial portography (CTAP) and intraoperative ultrasound (IOUS) in the management of patients with primary or metastatic liver tumors; to study the ability of CTAP to define resectability before laparotomy in these patients; and to study whether the omission of CTAP in the imaging algorithm resulted in a diminished resectability rate. Eighty-eight consecutive patients with primary or metastatic liver cancer who underwent CTAP and/or IOUS between January 1990 and December 1993 were reviewed. Thirty patients had both CTAP and IOUS and underwent 31 laparotomies (Group I). The sensitivity of these two tests to detect liver tumors was compared. Twenty-eight explorations were performed for hepatic metastases and three for hepatocellular carcinoma. Fifty-three patients, including those in group I, underwent CTAP before laparotomy and were studied to assess the sensitivity of CTAP in determining unresectability (Group II). Thirty-five patients (Group III) had IOUS only and were studied to determine whether the omission of CTAP decreased the resectability rate. In Group I, 52 hepatic lesions were found by a combination of imaging studies, operative exploration, and pathologic examination. The sensitivity of CT, CTAP, IOUS, and exploration were 67 per cent, 65 per cent, 100 per cent, and 75 per cent, respectively. IOUS was more sensitive than any other modality in detecting liver tumors (P < 0.001). It added new information in 7/31 cases (23%). The false positive rate of CTAP was 4/31 (13%). In one case (3%), a false positive result would have precluded a curative resection. CTAP changed management of 4/53 patients (7.5%) by showing unresectable disease.(ABSTRACT TRUNCATED AT 250 WORDS)