The aim of the present study was to Investigate the prevalence of tubular dysfunction and to assess the clinical significance of low-molecular-weight proteinuria and enzymuria. In children with insulin-dependent diabetes mellitus (IDDM). N.acetyl-beta-D-glucosaminidase (NAG) and beta-microglobulin (beta(2)M) excretion was determined in 52 children with insulin-dependent diabetes mellitus and 28 controls. Patients were grouped according to the duration of diabetes: group 1 (n = 7): less than one year; group 2 (n = 27): one to five years; groups 3 (n = 18): greater than five years. Both parameters were significantly Increased in groups 2 and 3 compared to controls. Urinary B2M levels correlated significantly with albuminuria and HbA(1C), while urinary NAG levels correlated only with HbA(1C).