ABSTRACT.Urinary albumin excretion (UAE) was determined by radioimmunoassay in two 24 h urine collections from 125 diabetic children and adolescents and from 71 normal children matched for age and sex. Thirteen patients (10.4%) aged>12 years had microalbuminuria, i. e. log transformed UAE levels above the upper normal range (24.5 mg/24 h). UAE values were positively correlated with age, GH secretion, but not with duration of disease, glycosylated hemoglobin, renal size or N‐acetyl‐beta‐glucosaminidase excretion. Diabetic normoalbuminuric children aged 10 years and older had significantly higher UAE than controls and than younger diabetic patients matched for duration of disease. HLA DR3/DR4 heterozygosity frequency was significantly higher (p<0.01) in the microalbuminurine group than in the normoalbuminuric. All microalbuminuric subjects (n=8) with short duration of disease (3.92 ± 3.43 yr) developed diabetes at puberty. In conclusion, our cross‐sectional study suggests: if a number of factors are combined, i. e. HLA DR3/DR4 heterozygosity, onset of disease at puberty and higher GH values, the probability of developing abnormal levels of UAE will