Over a 31-month period, 100 patients with malignant hepatic tumors were preoperatively evaluated with three imaging techniques. The results of intravenously enhanced computed tomography (CT) scan, selective hepatic arterial contrast CT, and magnetic resonance imaging (MRI) were compared with operative findings. A total of 227 lesions were identified, with the sensitivity for tumor detection being arteriographically enhanced CT 94% (p less than 0.01), MRI 70%, and CT 66%. This advantage for arteriographically enhanced CT was most marked for lesions less than 1 cm in diameter (82% versus 20% for MRI and 5% for CT; p less than 0.01). Arteriographically enhanced CT was also most sensitive in assessing tumor margins. MRI was clearly superior to arteriographically enhanced CT or CT in detecting vascular involvement (85% versus 30% and 8%, respectively; p less than 0.01). No imaging technique was sensitive in determining extrahepatic involvement. Arteriographically enhanced CT was also best at predicting the operative procedure. The combination of arteriographically enhanced CT and MRI was the best predictor of true disease. We conclude that both arteriographically enhanced CT and MRI should be used for preoperative assessment of hepatic malignancies.