HOHSTETER, M., I.-C. SOSTARI C -ZUCKERMANN, S. RELJIC, L. MEDVEN ZAGRADISNIK, B. ARTUKOVIC, Z. GRABAREVIC, J. KUSAK, D. HUBER, A. GUDAN KURILJ: Intestinal adenocarcinoma in a European brown bear (Ursus arctos) - a case report. Vet. arhiv 88, 569-579, 2018. This article presents the first case of intestinal adenocarcinoma in a free living, culled 12 year old, European female brown bear (Ursus arctos), with its characteristic macropathological and histopathological manifestations. Necropsy revealed thoracic gunshot injuries (compassionate shot) and the poor physical condition of the animal, with body fat loss and musculature atrophy. An infiltrative mass protruded the jejunal wall with infiltration of the mesentery, visceral and parietal peritoneum, and distal parts of the colon and rectum. The histopathological examination presented an infiltrative, unencapsulated, moderately cellular neoplastic mass, composed of an epithelial cell population, forming irregular nests, papillary and ribbon like structures and small number of tubules, surrounded by an extensive desmoplastic reaction. Within the tumor a small number of cysts filled with mucin were noted. The epithelial neoplastic cells exhibited mild anisocytosis and anisokaryosis, and a low mitotic index. Histochemical Van Gieson staining showed strong positivity in the desmoplastic proliferation. The epithelial tumor cells were positively imunostained with cytokerain, and stromal cells with vimentin. The histological features presented are characteristic of intestinal adenocarcinomas, of the mixed tubular and mucinous type, with a prominent scirrous reaction. Key words: intestinal adenocarcinoma; European brown bear (Ursus arctos); macropathology; histopathology; immunohistochemistry