Abstract: The peripheral blood natural killer(NK)cell activity,the percentage of E-C,bR rosettes, phagocytosis of neutrophil and lymphocyte blastogenesis were studied to assess the cellular immunoregulation in patients with advanced schistosomiasis.The results showed that the NK cell activity and the percentage of E-C,bR rosettes were significantly lower in patients with splenomegaly than in patients who had undergone splenectomy and in normal subjects.The phagocytic index of neutrophil and lymphocyte blastogenesis was reduced in patients with advanced schistosomiasis,but no significant difference was found between the patients with and without splenectomy.These results suggested that splenectomy not only reduce the portal hypertension but also improve the regulatory functions of cellular immunity which may enhance the patient's resistance against pathogens.