This study was designed to evaluate MRA imaging as a potential non-invasive method to study vascular infiltration in patients with abdominal neoplasms. Forty-three patients with abdominal tumors proven by CT and/or MRI were examined with MRA and subsequently with angiography. Of 15 cases of liver tumor, MRA allowed poor intratumoral vascularization to be demonstrated in 1 patient only, but it always provided a characteristic sign--i.e., the complete absence of flow in the hepatic segments infiltrated by the tumor and the evidence of pericapsular neovascularization. In 8 cases portal vein involvement was observed (4 cases of compression/dislocation, 2 cases of infiltration and 2 of thrombosis). In all cases MRA allowed the relationship between tumor and venous structures to be evaluated. It also demonstrated collateral vessel formations in 8 patients with cancrocirrhosis. Two cases of thrombosis and 3 infiltrations of the vena cava were demonstrated. Neither hepatic artery nor intrahepatic arterial vascularization could be correctly evaluated. Of 10 cases of renal tumors and in 3 of adrenal tumors, renal vein infiltration was seen in 4 cases and compression in 3, with only 1 false-positive finding. In these patients and in those with retroperitoneal masses, MRA provided valuable information on the relationship between tumor and vascular structures and was useful in detecting collateral vessels. In our experience, MRA is to be considered as a complementary technique to be performed after CT or MRI when additional information is needed as to the relationship between tumor and vascular structures. In the preoperative evaluation of abdominal neoplasm, angiography remains the gold standard, in spite of its invasiveness.