The porcine brain natriuretic peptide (BNP-26) and its analog, (Mpr4,D-Ala6,13) BNP(4-24)-NH2, were synthesized by solid phase method employing the Boc strategy. After HF cleavage to remove the protected groups, the crude linear peptide was air-oxidized under alkaline conditions to form the disulfide bridge. The synthetic peptides, purified by gel filtration and HPLC, were proved to have pharmacological spectra very similar to that of natural BNP such as natriuretic/diuretic, hypotensive and vaso-relaxant activities.