Mung-bean protein isolates were hydrolysed by two proteases alcalase and neutrase commercially available for food industry use, and the angiotensin I-converting enzyme (ACE) inhibitory activities of the enzymatic hydrolysates were measured at different hydrolysis times. The non-hydrolysed protein showed no inhibitory activity. Hydrolysates generated with neutrase displayed very low ACE inhibitory activity, while those obtained with alcalase exhibited high inhibitory activity. The highest ACE inhibitory activity with the IC 50 value of 0.64 mg protein/mL was found in the hydrolysate obtained with alcalase at 2 h of hydrolysis time. These results indicated that mung-bean protein is a good protein source of ACE inhibitory peptides when hydrolysed with the protease alcalase. The mung-bean protein hydrolysates prepared with alcalase might be utilised for physiologically functional foods with antihypertensive activity.