The Reg IV gene has been documented in the colon, small intestine, stomach and pancreas of the human. Expression of the Reg IV in different cell types has been associated with regeneration, cell growth and cell survival, cell adhesion and resistance to apoptosis. It is unknown whether the Reg IV protein is present in the normal rat tissue. The aim of this study was to reveal the expression of the Reg IV protein in the rat spleen and colon. Western blot analysis using antibody specific for Reg IV protein were performed on rat spleen and colon extracts. Low level of Reg IV expression was found in all examined colon samples. The expression of Reg IV protein in spleen tissue was significantly higher than in the colon. Reg IV protein was immunohistochemically stained in a few epithelial cells in the basal portion of colon crypts and in a large spleen cells which were scattered in the red pulp. Our results demonstrate for the first time the presence of the Reg IV protein expression in the healthy spleen and colon tissue of the rat. Other members of the Reg family, Reg I and Reg III proteins have been shown to act as a growth factors in gastrointestinal tract, but without further experiments we can only assume the potential role of the Reg IV protein in spleen and colon cell growth.