Based on renal arteriography, hypertensive patients were classified as (1) normal, (2) unilaterally significantly abnormal, and (3) borderline cases. Those who underwent surgery were classified as cured, improved, and unchanged. The results of renograms using iodohippurate sodium I 131 chlormerodrin Hg 197 renograms and renal scans were compared to rapid sequence intravenous pyelography (RSIVP). In group 1 (ten patients), there was one false-positive iodohippurate renogram and two false-positive RSIVPs. Chlormerodrin renograms and scans were normal. In group 2 (13 patients) all iodohippurate renograms and RSIVPs reflected the side of the arteriographic lesion. Of these, 12 were cured or improved surgically. Two false-negative chlormerodrin renograms and scans occurred. In group 3 (six patients), all iodohippurate renograms reflected the side of the lesion while two patients, one cured and one improved, had negative RSIVP. Chlormerodrin renogram and scan were each falsely negative once.