A study of renal disease in familial dysautonomia identified excess glomerulosclerosis in 10 or 13 autopsied and biopsied patients. Sympathetic nerve terminals could not be found on renal vessels in biopsied tissue; they were invariably demonstrable in controls. Altered renovascular responsivity to systemic hypotension in familial dysautonomia may lead to ischemia and subsequent sclerosis of glomeruli. Review of 79 living outpatients showed that clinically overt renal disease was rare in familial dysautonomia. Nevertheless, frequent observations of elevations of serum creatinine concentrations (32% of patients) and blood urea concentrations (76% of patients) indicated a high prevalence of abnormality. An association was found between hypotension and renal dysfunction.