Available data fail to define the prevalence of ischemic nephropathy or the association of critical renovascular disease (RVD) with renal function in the atherosclerotic population. The data do suggest, however, that critical RVD is prevalent and that the prevalence increases with age, increasing serum creatinine and clinical atherosclerosis at extrarenal sites. Furthermore, our preliminary data suggest that critical RVD may be either the cause or an important superimposed accelerant of renal insufficiency in a larger portion of the atherosclerotic population with renal insufficiency than previously recognized. In this latter group, critical RVD as a cause of renal insufficiency appears to be rapidly progressive and may contribute to end-stage renal disease with increasing frequency. Conclusive definition of the importance of ischemic nephropathy as a contributor to progressive renal insufficiency and end-stage renal disease will require population-based studies that estimate the prevalence of ischemic nephropathy and the natural history of the disease. Presently, renal duplex sonography appears to be the screening test of choice to define critical RVD for such population-based studies. (C) 1994 by the National Kidney Foundation, Inc.