Primary extranodal lymphoma of the liver is very rare, approximately thirty-one cases having been reported in the literature. We report one case of primary malignant lymphoma of the liver in a 26-year-old female, who was presented with palpable abdominal mass on the epigastrium for about 40 days. Laboratory findings revealed no specific abnormalities. Peripheral lymph nodes or spleen were not palpable. An abdominal ultrasonogram revealed a huge mass involving the entire left lobe of the liver. Left lateral segmentectomy of the liver was done. The resected lateral portion of left lobe of the liver showed a large solitary mass, 12 cm in the greatest dimension, with a yellowish gray fleshy solid cut surface. Though light microscopic feature was compatible with primary malignant lymphoma, diffuse large cell type, intermediate grade by the working formulation, undifferentiated carcinomas including hepatocellular carcinoma, plasmacytoma, and pleomorphic sarcomas could not be completely ruled out. Thus, marker studies and electron microscopic examination were performed. Immunoperoxidase stains for common leukocyte antigen was positive, and the Leder stain for myeloid granule was negative. Electron microscopic stuids revealed findings of neoplastic lymphoid cells, consistent with malignant lymphoma. Primary lymphoma of the liver has only rarely been reported, and its natural history is unclear. Many of the reported cases have been large cell lymphomas, as in this case.