It has been demonstrated by Smithers & Terry (8) that adult worms are destroyed when they are transferred to another host previously immunized by the first one. As is well known, the schistoroma antigen used in the schistosomiasis intradermal test is usually prepared from worms obtained with experimentally infected mice. This fact raised an important question in our mind: Could the antigen prepared from mice worms bring with it some of the host antigens? If this is so, the host antigens contaminate the S. mansoni antigen and would interfere with the specificity of the test. Shistosoma antigens from worms removed by portal blood perfusion during splenectomy of human patients, were prepared and tested side by side, using the well-known antigen prepared from mice in Brazil by Pellegrino. 73 patients without any other parasitosis were tested using both kinds of antigen at the same time, and 29 individuals without the parasitosis were used for control. From table l, we can see that the antigen gave a large size papule with 100% positive, compared with the smaller human antigen, but showed a percentage of 52%, false positive. In the patients tested with antigen from human S. mansoni worms the positivity was 90% and the false cases dropped to 27%. Looking at table 2, (relationship to the allergic factors) one can see that mize antigen gave more positive results in 39 patients without an allergic background. On the other hand in the control group without schistosomiasis and with allergic manifestation the average tize of the papules was positive for the mice S. mansoni antigen and negative for the human S. mansoni antigen. In conclusion, it has been demonstrated that average size of the papules of both antigen were smaller when the antigen from worms of the human host was used. At same time, the allergic patients condition gave papule bigger than the nonallergic patients. The authors admit that in a region with endemic schistosomiasis where could be a great number of individuals showing a bordeline size of papule, this fact has been demonstrated in the paper, as a result of anti-species antigen-anti body reaction.