Albuminuria is a risk factor for renal and cardiovascular disease. We conducted a cross sectional survey of 4549 older American Indians in Arizona, Oklahoma and North and South Dakota of (micro)albuminuria. A range of 20.1 to 48.3% of all participants had either micro- (> or = 30 to < 300 mg albumin/g creatinine) or macroalbuminuria (> or = 300 mg albumin/g creatinine). A total of 53% of the participants were diabetic, and the prevalence in Arizona (65 to 70%) was significantly greater than the other two sites. Prevalence of micro- and macroalbuminuria were significantly higher among those who were older, diabetic or hypertensive, and participants from Arizona. Even normotensive, nondiabetic Arizona Indians had higher prevalence rates than similar participants elsewhere. Higher prevalence rates of micro- and macroalbuminuria were also found among Arizona participants than participants with similar degrees of glucose intolerance from the other two sites. Indians reporting the greatest degree of Indian blood were more likely to have abnormal albuminuria (P < 0.0001). The duration of diabetes, fasting plasma glucose, systolic blood pressure, fibrinogen and Indian heritage were independently associated with micro- or macroalbuminuria. The association of albuminuria with subsequent ESRD, cardiovascular morbidity and overall mortality suggests that these American Indians will face a large disease burden. The correlation with reported Indian blood implies a strong component of genetic susceptibility, possibly independent of diabetes.