A novel antimicrobial peptide, SRTAP-40 has been purified and characterized from sheep reproductive tract. The isolation procedure entailed acetic acid extraction, gel filtration chromatography, and HPLC. SRTAP-40 is composed of 40 amino acid residues with a MW of 4,820.47 Da from MALDI-TOF-MS. Its N-terminal sequence was AYVLDEPKP. SRTAP-40 cDNA was cloned by 3'-RACE. SRTAP-40 showed activity against E. coli Staphylococcus aureus, Streptococcus sp. and, Candida albicans with MIC values of 12, 12, 24, 6 mu g/ml, respectively. By BLAST search, SRTAP-40 had no significant similarity to any known peptide.