A stimulation clonidine test was performed in children for a study of STH secretion. The drug was injected at a dose of 0.15 m per 1 m2 of body surface. A total of 47 children were investigated. Of them 21 were healthy, with normal growth and 26 with constitutional retardation of growth (CRG). Maximum values of STH secretion were observed 60-90 min. after clonidine administration. Mean values of a STH secretion peak exceeded the initial ones greater than 8-fold in both groups without significant differences between them. Side-effects were insignificant and of transient nature. Thus clonidine is a sensitive, easy to use and safe stimulator of STH secretion. We revealed no difference in STH secretion between children with normal growth and those with CRG.