Growth hormone (GH) and insulin-like growth factor-I (IGF-I) metabolism may be disturbed in obese children. We investigated serum GH, IGF-I, IGF-binding protein-3 (IGFBP-3) levels in 42 obese and 40 non-obese healthy children aged 6-14 years. GH stimulation tests with L-dopa and insulin were performed. Serum IGF-I levels were studied by immunoradiometric assay (IRMA) and IGFBP-3 levels by radioimmunoassay (RIA). IGF-I levels were significantly higher in the obese group (p < 0.05), but IGFBP-3 levels were not different from the control group. IGF-I and IGFBP-3 levels were significantly higher in the obese pubertal children than in the obese prepubertal ones (p < 0.05). A positive linear correlation was found between body mass index (BMI) and IGF-I levels (r = 0.51, p < 0.05). These results suggest that obesity may have a considerable effect on IGF-I.