Laboratory infection studies involving Bulinus species from the area of the South Chad Irrigation Project, Borno State, Nigeria, were performed using Schistosoma haematobium obtained during a survey of schistosome and intestinal helminth infections in pupils at a local secondary school. These revealed the presence of both typical truncatus and africanus borne strains of the parasite with the former developing in Bulinus rohlfsi and the latter in one of two populations of B. globosus the Ngala population). The forskali group snail, B. senegalensis, was susceptible to infection with both parasite strains, while B. globosus Lake Chad failed to become infected with either. Investigations into the development and productivity of S. haematobium, and the effects of infections on the growth and reproductive biology of intermediate hosts, revealed that although initial establishment of an infection in a given bulinid depended on the strain to which it had been exposed, there was no correlation between parasite strain and subsequent interactions. Observed differences between each bulinid/ schistosome combination depended on the species of host involved, and could be linked with aspects of the mollusc's biology. B. globosus Ngala exposed to compatible S. haematobium produced long-lived infections. Detailed studies of the changes in cercarial output and host oviposition over the course of the infection in this case showed patterns that were not evident in the other shorter lived species. Laboratory experiments revealed that immature schistosome infections were capable of surviving in aestivating B. senegalensis for periods of 56 days, developing to release cercariae after snails were revived. Morphological comparisons of the susceptible B. globosus Ngala and refractory Lake Chad populations showed significant differences in the dimensions of their male copulatory organs. Breeding experiments, however, -proved that members of the two populations are capable of successful cross-fertilization.