Sequences of three cDNAs of Schistosoma japonicum are presented. Two of them code for the antigens Sj32 (hemoglobinase) and cathepsin B. The third clone represents a mutant derivative of the cathepsin B gene. The DNA and amino acid sequences are compared to their homologues from S. mansoni. The mutant cathepsin B, in which the Cys29 in the active center is replaced by Ser, is discussed with respect to a possible function.