We studied urinary albumin excretion in 2 different groups of teenage diabetics, one with HbA1 less than 10% (n = 15) and another with HbA1 greater than 13% (n = 17). We found a highly significant difference between the 2 groups regarding the albumin excretion rate (AER) in overnight urines. Median value 15.8 micrograms/min (range 4.9-80.5) and 4.2 micrograms/min (range 1.0-12.6) in the high and low HbA1 group respectively. In a reference group of 19 healthy teenagers, the median AER was 4.9 micrograms/min (range 0.5-15.0). 59% of the patients in the high HbA1-group had values above the upper range in the reference group, 15 micrograms/min, and one had positive Albustix. In contrast, no difference in AER was observed between the low HbA1-group and the reference group. We did not find any correlation between AER and duration of diabetes, but the one patient with gross proteinuria had had diabetes for 14 years. No significant difference between the groups regarding blood pressure or retinopathy was found. Thus, AER was elevated in a large proportion (59%) of poorly regulated diabetic teenagers regardless of diabetic duration. This fact questions the value of employing moderately elevated urinary albumin excretion rate in teenage diabetics as a marker for later development of clinical diabetic nephropathy.