Thirty patients suffering from active intestinal S. mansoni infection, were classified into 3 groups. The first group: 13 cases with early active intestinal schistosomiasis without hepatosplenomegaly. The second group: 11 cases with hepatosplenomegaly and the third group: 6 cases with splenomegaly and ascites. Also 10 normal individuals were included as a normal control group. Histopathological examination of rectal mucosa showed hyperaemia with extravasation of blood in early cases and granulomatous lesions in the second group with hepatosplenomegaly. The structural changes were severe in the late ascitic group. In this group the rectal mucosal glands showed distorted irregular tubular branching in addition to the granulomatous and the fibrous reactions. Histochemical studies including periodic acid schiff, alkaline phosphatase and acetyl cholinestrase reactions were done. Using the periodic acid shiff stain, the goblet cells showed strong reaction for neutral mucin in cases of group I (early cases) and group II (late hepatosplenomegalic cases). In group III (late ascitic cases) the goblet cells were faintly stained. A notable difference was observed between the lightly and heavily infected patients of this group. No alkaline phosphatase reactivity could be identified in rectal crypts of patients and controls. Alkaline phosphatase reactivity was sharply localised in S. mansoni egg shell. There was obvious decrease in the acetyl cholinesterase stained nerve fibres in the rectal mucosa of all studied patients. The decrease was more in chronic and heavily infected cases rather than in the acute and lightly infected ones.