The clinical, morphologic, and follow-up findings in 32 patients with a hitherto rarely reported tumor of the liver are reported. The study comprised 20 women (62.5 per cent) and 12 men (37.5 per cent) ranging in age from 19 to 86 years (average, 49.65 years). The tumors were discovered incidentally in four patients (12.5 per cent). Four patients (12.5 per cent) had jaundice attributable to the tumors; one of these patients experienced liver failure. One patient presented with an acutely painful abdomen due to hemoperitoneum. The remaining patients had nonspecific complaints. Grossly, the tumors were often multiple and involved both lobes of the liver. They were generally white and firm to hard. Microscopically, the neoplastic cells infiltrated sinusoids and intrahepatic veins of all sizes. Two types of tumor cells were identified--dendritic and epithelioid. Tumor cells were also vasoformative and synthesized Factor VIII-related antigen. Nine patients survived five years or longer. Two of these patients were alive five years, two nine years, one 12 years, and one 15 years after the onset of disease. Three patients died seven, ten, and 28 years, respectively, after the initial diagnosis. This vascular tumor has distinctive morphologic features that allow differentiation from sclerosing carcinoma and angiosarcoma. Although the prognosis is much more favorable than that for angiosarcoma, extrahepatic metastases occurred in nine of the patients (28 per cent) in this series. The biologic behavior of the tumor may be related in part to its matrix, which may show inflammation, dense sclerosis, and calcification.