In 110 primary hepatic neoplasms in the dog, 15 carcinoids were diagnosed. Diffuse involvement of all liver lobes with severe hemorrhage and necrosis was seen in all cases. The neoplasms had three distinct histologic patterns: solid nests, cords or ribbons; and an alveolar pattern with rosettes. In all three groups there was fibrovascular stroma that was hyalinized, mineralized, and thick in some places. The neoplastic cells were relatively uniform, polygonal to spindle-shaped, with eosinophilic, granular cytoplasm and vesiculated nuclei. Mitotic activity varied among the three groups. Argyrophilia was seen in all specimens stained with modified Grimelius stain. Metastasis occurred in 14 of 15 dogs (93.3%); the peritoneal wall and adjoining lymph nodes were the most common sites.