In 1989 a nation-wide investigation of blood pressure and urinary albumin excretion rate (AER) was carried out in 506 boys and 441 girls with Type 1 diabetes (approximately 80% of total) treated at 22 paediatric departments. In addition a reference population from 1979 consisting of 663 healthy non-diabetic children (334 boys, 329 girls) served as a control group with respect to blood pressure and body mass index. Microalbuminuria was defined as AER of 20-150 micrograms min-1 in at least two out of three timed overnight urine collections and was diagnosed in 30 adolescents (16 boys, 14 girls). Five patients (3 boys, 2 girls) had overt proteinuria (AER: > 150 micrograms min-1). Age-related percentile charts based on one blood pressure reading were provided for normoalbuminuric diabetic patients and the healthy control group. The study revealed an increase in arterial blood pressure during the period of the pubertal growth spurt for the diabetic and non-diabetic group. The changes were most pronounced for systolic blood pressure. No statistically significant difference was observed in systolic and diastolic blood pressure between normoalbuminuric diabetic children and healthy control children. However, diabetic females aged 15-18 years had significantly higher diastolic blood pressure (75 +/- 1 mmHg, n = 139, mean +/- SE) than healthy control females (72 +/- 1 mmHg, n = 155, p < 0.01), and significantly (p < 0.001) higher body mass index (diabetic females: 22.3 +/- 0.2 kg m-2 vs healthy females: 20.9 +/- 0.2 kg m-2, mean +/- SE.(ABSTRACT TRUNCATED AT 250 WORDS)