Nineteen cases of proven hepatic alveolar echinococcosis were examined by magnetic resonance (MR) and the results were compared with CT. Fibrous and parasitic tissue showed low signal both on T1- and, generally, on T2-weighted images. In a few cases a high signal on T2-weighted images may be observed, due either to central necrotic zones or to small peripheral cysts. Central necrosis was more easily identified by MR than by CT. However, MR seemed to be less effective than CT in allowing us to reach a positive diagnosis, due to its inability to show microcalcifications. In addition, MR may not reveal small lesions. In most cases T1-weighted images revealed more clearly than CT did the margins of the lesions and the hepatic extension, especially to hepatic veins, vena cava, and perihepatic spaces.