Plasma B-Endorphin (B-EP), Growth Hormone (GH) and cortisol response to 100 mcg/m2 b.s., i.v. clonidine (an alpha 2-adrenergic agonist) were evaluated in 17 normal weight children (8 prepubertal and 9 pubertal) and in 15 children with simple exogenous obesity (7 prepubertal and 8 pubertal, weight excess ranging from 29% to 97%). All the hormones were measured by radioimmunoassay either directly in the plasma (GH and cortisol) or after extraction and chromatography (B-EP). Obese prepubertal and pubertal children showed basal B-EP levels significantly higher than in controls and no differences were found in GH and cortisol levels. While in controls clonidine stimulated a significant release of plasma GH and B-EP in obese patients, irrespective of pubertal development, no changes were found. Cortisol levels decreased in both groups. These data suggest an impaired adrenergic control of GH and B-EP secretion in children with simple exogenous obesity.