The prevalence of microalbuminuria in younger-onset diabetic participants in a large population-based study of diabetic retinopathy was determined, and the relationships of microalbuminuria to blood pressure and other risk factors were investigated. Using an agglutination inhibition test (AlbuScreen), the frequency of microalbuminuria was 21.2%. To evaluate the association of several characteristics with the presence of microalbuminuria, multivariate models based on logistic regression were developed. Microalbuminuria was associated with having higher systolic or diastolic blood pressure and higher glycosylated hemoglobin. These findings give further impetus to efforts to reduce controllable risk factors in younger-onset diabetic persons.