The urinary levels of albumin, beta 2-microglobulin (BMG) and beta-D-N-acetyl glucosaminidase (NAG) were studied in 30 children with short stature due to partial or complete growth hormone (GH) deficiency under treatment. All 30 children had a normal urinalysis and no clinical evidence of renal disease. They were treated with recombinant GH in a dose of 0.5 IU/kg/week given subcutaneously. The mean albumin excretion rate (9.13 +/- 8.33 micrograms/min/1.73 m2) of these children was significantly higher than that (4.2 +/- 2.27 micrograms/min/1.73 m2) of 30 age-, sex- and pubertal status-matched normal children (p < 0.01). BMG and NAG excretion was normal in both groups. There was no correlation between the urinary albumin excretion rate and the duration of GH treatment. Among the GH-treated children, the urinary albumin excretion rate was correlated significantly with circulatory insulin-like growth factor I (IGF-I) (r = 0.65, p < 0.01). In 7 other children analyzed before and three months after start of GH treatment, the mean urinary albumin excretion rate increased significantly from 4.71 +/- 3.95 micrograms/min/1.73 m2 to 8.29 +/- 2.70 micrograms/min/1.73 m2 (p < 0.03). These results suggest the possibility of functional glomerular alterations during GH therapy.