The ability of adherent and nonadherent peripheral blood mononuclear cells (PBMC) from forty patients with schistosomiasis to produce IL-1 and IL-2 was studied. The results indicated that ConA-stimulated nonadherent-PBMC from patients exhibited a decreasing ability to produce IL-2 compared with controls (P less than 0.001), and that their ConA-activated blast cells expressed a smaller number of cell surface IL-2 receptor since IL-2 adsorption to the patient cells was lower than that to the normal cells (P less than 0.01). On the other hand, IL-1 production by LpS-stimulated adherent-PBMC from the patients was in agreement with that from the normal controls (P greater than 0.05). From above results, it seems that human organism following infection of Schistosoma japonicum might display a sort of suppressive phenomenon in the production of and the response to IL-2.