This report synthesizes the literature and the authors' experience in the use of angiotensin-converting enzyme-inhibited renography for the diagnosis of hypertension associated with critical renal arterial disease. The pathophysiology underlying the performance of the test and its interpretation are provided. The test is not a screening test of patients with hypertension. The need for preselection of patients is emphasized. The differences in using glomerular versus tubular radioisotopic agents are identified. Patient preparation, testing procedure, and interpretation of the data are reviewed. Clinical conditions, other than those in which hypertension is associated with critical disease of the main renal artery, in which false-positive renographic tests have occurred, are listed.