The amount of immunoglobulins serum and the cutaneous sensitivity to specific antigen in 19 patients with intestinal schistosomiasis were determined, as an attempt to study the incidence of delayed and imediate type of hypersensitivity. The tests were performed before and thirty, sixty and ninety days after treatment with aminonitrotiazol. The immunoglobulin levels before treatment were found to be 1,893 ± 472, 186 ± 74 and 91 ± 26 mg%, respectively for IgG, IgA and IgM; ninety days after treatment the level for IgG became normal (1,266 ± 389 mg%) and a slight increase of IgA (270 ± 89 mg%) and IgM (111 ± 31 mg%) was observed. The patients were intradermally tested with schistosomin and with anti IgE serum. The tests before treatment gave the following resulta: 1.22 ± 0.36 cm² for schistosomin and 1.04 ± 0.25 cm² for anti IgE. Ninety days afterwards a slight increase of the reactions was observed and the results respectively were 1.42 ± 0.65 cm² and 1.15 ± 0.32 cm². The studies for delayed hypersenstivity indicated that 35% of patients showed an area of induration larger than 0.5 cm², 48 hours after the intradermal injection with schistosomin, and 71% developed positive reaction when challenged with dinitrofluorobenzene