Application of immunocytochemical methods (DP, IP, PAP, APAAP and IP-IP) has confirmed the existence of p27 and gp70 feline leukosis viral antigens (FeLV) in various tissues of 22 cats. Both viral antigens were found in bone marrow stem cells, but p27 antigens were mostly found in epithelial cells of intestinal crypts. In splenic T-lymphocytes and mediastinal lymph nodes the predominance of gp70 antigens in FeLV was confirmed, while the tropism of leukosis viruses in the lung was inclined to epithelial cells of bronchial glands where p27 antigens were dominant.