Studies of the pathogenesis of schistosomal infections have revealed that the occurrence of disease is so strongly related to host responses to parasite products, that schistosomiasis can be considered as an immunological disease. Further, numerous genetic and environmental factors may modify the host resistance or susceptibility to disease. To test whether hepatosplenic patients manifest different immune capabilities, and the effects of intensity of infection on immune responses; we evaluated anti-SMW68 and anti-crude antigens (SWAP & SEA) antibody levels in 100 children aged 9-15, having light and moderate S. mansoni infection (80-360 eggs/gm of stool). In this group, anti-SMW67 antibody levels (determined by ELISA) were significantly higher in those with lower levels of infection (P less than 0.001). Furthermore, the hepatosplenic patients showed a lower anti-SMW68 antibody levels than those with intestinal schistosomiasis. (P less than 0.05). We conclude that the worm burden and so the resultant morbidity may be influenced by the immune capabilities of the host. Whether enhanced antibody response to SMW68 represents acquired protective humoral immunity remains to be determined.