Analysis of 234 separate function studies in unselected hypertensive patients yielded nine patients with patterns of occlusive main artery disease and 43 patients with a pattern of segmental artery disease. Their normal aortograms suggest that asymmetrical nephrosclerosis accounted for these patterns in all but three of the first group and in all but one of the second group. Surgical failures in the past include numerous instances of incorrect diagnoses based on asymmetric (positive) results of separate function tests. In contrast, renal vein renin activity measurements in the present study correctly predicted three surgical cures and six surgical failures. Such measurements are clearly superior to peripheral vein renin measurements and represent the best available method for diagnosing surgically correctible, ie, renin-dependent renovascular hypertension.