Hydrolysates of peanut protein from low denatured peanut dregs, which inhibit the angiotensinⅠconverting enzyme (ACE) were prepared by enzymic hydrolysis with Alcalase and N120p that are two proteases available for industrial use. Combination of Alcalase and N120p hydrolyzed peanut proteins most efficiently and the hydrolysates showed the most high activity (IC50=0.548 mg/ml). Sequential ultrafiltration of the hydrolysates with MW cut-off 10, 5 and 1KD resulted in increased activity of each filtrate up to IC50 of 0.255 mg/ml. Sephadex G-15 gel chromatography of the oligopeptides below MW 1KD eluted a peptide fraction of the most potent activity (IC50=0.091 mg/ml). the oligopeptide below MW 1 KD competitively inhibited ACE and it was evaluated for antihypertensive effect in spontaneously hypertensive rats (SHRs) following oral administration. Systolic blood pressure (SBP) significantly decreased after peptide ingestion and higher dose of peanut oligopeptides could not induce occurrence of low blood pressure.