ObjectiveSubjects with multiple renal arteries have been shown to suffer more frequently from hypertension and to have higher blood pressures than subjects whose kidneys are supplied by single renal arteries. This study was carried out to determine whether subjects with multiple renal arteries also have higher renin activity.MethodsWe studied 62 consecutive patients who had undergone angiography for various reasons. They were divided into two groups. Group A comprised 29 patients whose kidneys were supplied by single arteries (male:female ratio 1.63, mean age 51.8 ± 1.9 years) while Group B comprised 33 patients with multiple renal arteries (male:female ratio 2, mean age 47.3 ± 2.3 years).ResultsBefore stimulation with frusemide, the plasma renin in Group A was 0.79 ± 0.13 ng angiotensin I/ml per h, while in Group B the corresponding figure was 1.73 ± 0.38 ng angiotensin I/ml per h. This difference was statistically significant (P= 0.0127). Thirty minutes later the plasma renin level in Group A was 2.43 ± 0.37 ng angiotensin I/ml per h versus a level of 3.86 ± 0.53 ng angiotensin I/ml per h in Group B (P=; 0.0169). Again, 30 minutes later the level was 2.59 ± 0.4 ng angiotensin I/ml per h in Group A, versus 3.7± 6 0.59 ng angiotensin I/ml per h in Group B (P=; 0.0495).ConclusionsWe conclude that patients with multiple renal arteries constitute a group who have high plasma renin activity and may therefore be prone to develop arterial hypertension.