A subtractive cloning strategy has been applied for the identification of two cDNA clones whose corresponding transcripts were elevated in Schistosoma mansoni-resistant (BS-90) compared to susceptible (M-line) snails. Clone pBS11 encoded a 1.9-kb transcript that was more elevated compared to a 500-bp transcript encoded by clone pBS12. Consequently, more attention was focused on the molecular characterization of clone pBS11. Results showed that the transcript encoded by this clone was expressed in the albumen gland and was developmentally regulated. Sequence analysis of pBS11 demonstrated the presence of an open reading frame that corresponded to a novel Biomphalaria glabrata albumen gland gene product. Comparative Southern analysis of the resistant and susceptible snail lines using pBS11 as probe indicated the presence of a BamHI and EcoRI RFLP between the two strains.