Schistosoma mansoni signal transduction pathways are promising sources of target molecules for the development of novel control strategies against this platyhelminth parasite of humans. Members of the protein kinase C (PKC) family play key roles in such pathways activated by both receptor tyrosine kinases and other receptors, controlling a variety of physiological processes. Here, we report the cloning and molecular characterization of the first PKC identified in S. mansoni. Structural analysis indicated that SmPKC1 exhibits all the features typical of the conventional PKC subfamily. The gene structure was determined in silico and found to comprise a total of 15 exons and 14 introns. This structure is highly conserved; all intron positions are also present in the human PKCbeta gene and most of the exon sizes are identical. Using PCR on genomic DNA we were able to show that putative orthologues of SmPKC1 are present in 9 Schistosoma species. SmPKC1 expression is developmentally regulated with the highest level of transcripts in miracidia, whereas SmPKC1 protein expression is higher in the sporocyst. The localization of SmPKC1 on the sporocyst ridge cyton and in schistosomula acetabular glands suggests that the enzyme plays a role in signal transduction pathways associated with larval transformation.