AbstractIntermediate hosts ofSchistosoma haematobium, the causative agent of urinary schistosomiasis, in Lake Malaŵi include:Bulinus globosus, a member of theB. africanusgroup andB. nyassanus, a diploid member of theB. truncatus/tropicusspecies complex. We compared genetic variability between isolates ofS. haematobiumfrom the southern part of the lake (Cape Maclear), where bothB. globosusandB. nyassanusplay a role as intermediate hosts, and isolates from the northern part, where onlyB. globosusis host. Data show that theS. haematobiumisolates from these two areas of Lake Malaŵi cannot be distinguished using nuclear or mitochondrial sequences and are capable of cross-infections.