(4S)-1-Alkyl-3-[[N-(carboxyalkyl)amino]acyl]-2-oxoimidazolidine-4- carboxylic acid derivatives (3) were prepared by two methods. Their angiotensin converting enzyme (ACE) inhibitory activities and antihypertensive effects were evaluated, and the structure-activity relationships were discussed. The dicarboxylic acids 3a-n possessing S,S,S configuration showed potent in vitro ACE inhibitory activities with IC50 values of 1.1 X 10(-8)-1.5 X 10(-9) M. The most potent compound in this series, monoester 3p, had an ID50 value of 0.24 mg/kg, po for inhibition of angiotensin I induced pressor response in normotensive rats and produced a dose-dependent decrease in systolic blood pressure of spontaneously hypertensive rats (SHRs) at doses of 1-10 mg/kg, po.