Idiopathic nodular glomerulosclerosis (ING) is an enigmatic condition that resembles nodular diabetic glomerulosclerosis but occurs in nondiabetic patients. We reviewed clinicopathologic features, immunohistochemical profiles, and outcomes in 23 patients with ING diagnosed from among 5,073 native renal biopsy samples (0.45%) at Columbia University from January 1996 to March 2001. This cohort, in which diabetes mellitus was excluded, consisted predominantly of older (mean age, 68.2 years) white (73.9%) men (78.3%). Clinical findings at presentation included renal insufficiency in 82.6% (mean serum creatinine = 2.4 mg/dL), proteinuria (> 3 g/d in 69.6%; mean 24-hour urine protein = 4.7 g/d), and-less frequently-full nephrotic syndrome (21.7%). There was a high prevalence of hypertension (95.7%; mean = 15.1 +/- 3.4 years), smoking (91.3%; mean = 52.9 +/- 6.9 pack-years), hypercholesterolemia (90%), and extrarenal vascular disease (43.5%). All 23 patients had prominent diffuse and nodular mesangial sclerosis, glomerular basement membrane thickening, arteriosclerosis, and arteriolosclerosis. Immunohistochemical staining for CD34, a marker of endothelial cells, showed an increased number of vascular channels within ING glomeruli compared with normal controls. Follow-up data were available for 17 patients, 6 of whom reached end-stage renal disease (ESRD) (35.3%). By Kaplan-Meier estimates, the median time after biopsy to ESRD was 26 months. Predictors of progression to ESRD included continuation of smoking (P =.0165), lack of angiotensin II blockade (P =.0007), degree of tubular atrophy and interstitial fibrosis (P =.0517), and degree of arteriosclerosis (P =.0096). In conclusion, ING is a progressive vasculopathic lesion linked to hypertension and cigarette smoking. Copyright 2002, Elsevier Science (USA). All rights reserved.