Renin inhibitor-1 (compound 26) is a potent and orally active renin inhibitor with IC 50 s of 0.9, 1.8 nM for rh-renin and hPRA, respectively. Renin inhibitor-1 shows antihypertensive efficacy. Renin inhibitor-1 has the potential for the research of hypertension and cardiovascular/renal diseases.