Microalbuminuria is associated with progression to renal disease in insulin-dependent diabetes and with increased mortality in noninsulin-dependent diabetes. In contrast, few studies have addressed the effect of microalbuminuria on cardiovascular risk in nondiabetics. We, therefore, determined the level of microalbuminuria in 316 nondiabetic subjects from the San Antonio Heart Study, a population-based study of diabetes and cardiovascular risk factors. Microalbuminuria (greater than or equal to 30 mg/l) was found in 42 of these 316 subjects (13%). Subjects with microalbuminuria had significantly higher blood pressure, triglyceride concentration, sum of insulin concentrations during a glucose tolerance test, and prevalence of hypertension and of self-reported myocardial infarction than subjects without microalbuminuria. When subjects with hypertension were excluded (n = 27), normotensive subjects with microalbuminuria (n = 31) still had significantly higher triglyceride concentrations and insulin sum than normotensive subjects without microalbuminuria (n = 258), suggesting that an increased atherogenic risk factor pattern exists even in normotensive subjects with microalbuminuria. Microalbuminuria may be a marker for cardiovascular risk, although it is not certain whether microalbuminuria causes these metabolic changes or results from some metabolic disturbance such as insulin resistance.