Evaluation of GH secretion is difficult because of fluctuation of basal serum GH levels and of GH release after pharmacological tests (PT). Serum IGF-1 and IGFBP-3 have been recently used as indicators of GH secretion. The purpose of this work was to compare serum levels of IGF-1 and IGFBP-3 with GH response to PT before surgery in 19 patients with tumors of the CNS, localized to the sellar and suprasellar regions. To define control values, serum IGF-1 and IGFBP-3 were determined in 111 normal males and in 63 normal females and percentile (p) distribution between chronological age (CA) 0.16 and 16 years(y) were established. Patients were divided as a function GH response to PT in 2 groups (Gr), Gr1 (n=11) with GH≥ 7 ng/ml and CA 7.84±4.24 y, and Gr2 (n=8) with GH<7ng/ml and CA 11.55±4.39 y. In Gr1, 3/11 had serum IGF-1 <3p and 7/11 serum IGFBP-3<3p. In Gr2. 8/8 had both IGF-1 and IGFBP-3<3p. Height SDS was significantly lower in Gr2 than in Gr 1(-2.54±1.59 and -0.93±1.25, respectively, p=0.02). On the other hand, in 11/19 patients with IGF-1 and IGFBP-3<3p, height SDS was significantly lower than in the other 8/19 patients (-2.24±1.44 and-0.84±1.43, respectively, p<0.05). It is concluded that determination of serum levels of IGF-1 and IGFBP-3 in a single sample is as good an indication of GH deficiency as 2 PT.