1. cDNA clones encoding antimicrobial guinea-pig neutrophil cationic peptides, GNCP-1 and GNCP-2 were isolated from a bone marrow cell cDNA library. 2. Three kinds of cDNAs (GNCP-1A, GNCP-1B and GNCP-2 cDNAs) were obtained, and the analysis of these cDNAs indicated that GNCPs were produced as precursor proteins comprising 93 amino acid residues, which were composed of signal sequences (N-terminal 19 residues), pro-peptide sequences (43 residues) and mature GNCP sequences (31 residues). 3. The deduced amino acid sequences showed that GNCP-1A and GNCP-1B differed by only one amino acid substitution in the pro-peptide region, and GNCP-1B and GNCP-2 differed by only one amino acid substitution in the mature peptide region. The nucleotide sequences of these cDNAs were highly homologous (99%). 4. Together these observations indicate that GNCPs are encoded by at least three kinds of mRNA transcripts which are likely derived from the similar genes.