The Schistosoma mansoni gene sequence encoding the breast basic conserved protein 1/ribosomal protein L13 has been isolated from an adult worm cDNA library using the Expressed Sequence Tag strategy. The cDNA codes for a putative protein of 184 amino acids which is approximately 55% identical to other eukaryotic L13 ribosomal proteins. A PCR amplified genomic fragment containing the coding region of the gene was seen to possess only a single large intron interrupting the open reading frame. Studies of gene expression by RT-PCR showed the transcript is expressed in distinct stages of the parasite life cycle. The cDNA was also hybridized with an ordered cosmid library of S. mansoni and the identified cosmids were mapped to chromosomes 3 and W by chromosomal in situ suppression hybridization.