Chronic effects on blood pressure of SQ29,852 administered daily for 21 consecutive days were compared to those of captopril and enalapril in spontaneously hypertensive (SHR) and two-kidney-one-clip renal hypertensive (CLIP) rats. 2. SQ29,852 showed significant chronic anti-hypertensive effects at 30 mg/kg in SHR and at 10 mg/kg in CLIP rats. Chronic anti-hypertensive effects of SQ29,852 were in-between those of enalapril and captopril. 3. Significant anti-hypertensive effects lasted in enalapril-treated SHR for 7 days after discontinuation of treatment, while only a tendency toward persistence of anti-hypertensive effects was noted in all animals treated with SQ29,852 and captopril.