The microscopical appearance of rat splenic tissue has been examined after subcutaneous transposition of the spleen and after portal vein ligation in rats subjected to splenic transposition. The histological picture was compared to that of control animals. Apart from congested red pulp and capsular fibrosis in the subcutaneous position did not seem to result in serious histological changes in the spleen. In three patients treated with subcutaneous transposition of resected spleen because of portal hypertension, histological needle biopsies from the splenic tissue were made postoperatively. Principally the same histological changes were found in the clinical as in the experimental material.