Lipomatous tumors of the liver are exceedingly rare. We report a case of lipoma of the liver, which is the smallest one ever detected by ultrasonography (US). A 50-year-old woman was admitted to our hospital on March 26, 1985, because of colicky epigastralgia. Laboratory data on admission revealed mild liver function abnormality, elevated serum CEA (27.0 ng/ml) and CA19-9 (46 U/ml) levels and a normal AFP level. US demonstrated a regular, round, homogeneous and hyperechoic lesion about 2.5×2.5 cm in diameter in the antero-superior segment of the liver. A displacement of the posterior diaphragm and faint posterior echo enhancement were also observed. CT showed, without enhancement by means of arterial infusion dynamic study, a clearly demarcated round low-density area (-28 HU). An avascular mass was revealed by angiography and also a cold nodule was obtained by scintigram. The lesion was diagnosed as a lipoma of the liver. In addition, giant tumors coexisted, which were diagnosed as massive hepatoma by radiographic and echographic findings. Despite injection therapy with intra-arterial anti-tumor agents, she died on the 124th hospital day. At autopsy, a solitary, round, well defined, encapsulated, soft and grey-white nodule, measuring 2.2×2.2×1.0 cm, was found in the liver parenchyma of the right lobe. Histologically, the tumor was a lipoma of the liver. And massive hepatoma (Edomondson II-III type) coexisted based on liver cirrhosis. On analysis of lipomatous tumors, which have been reported by us and others, echographic characteristics are (1) invariably hyperechoic mass, (2) variant posterior echo level, and (3) halo, which means a capsule of the tumor. It is concluded that lipomatous tumor should be taken into consideration when hyperechoic lesions are detected by US.