Growth hormone-binding protein (GHBP) was studied in 11 girls with true precocious puberty, aged 7.3 ± 0.2 years (mean ± SE), before and after the first 6 months of treatment with luteinizing hormone-releasing hormone analogue D-Trp<sup>6</sup>-LHRH. The <sup>125</sup>I-human GH was incubated with 150 µl of serum, bound and free GH were separated by gel filtration. The levels of GHBP increased significantly from 24.2 ± 1.3 to 28.1 ± 1.9% (p < 0.002, paired t test), more than expected for the normal age-dependent increase. The efficiency of LHRH-A therapy was confirmed by a decrease in growth rate and normalization of clinical and biological parameters. Our data agree with the hypothesis that the pubertal spurt is mediated by a sex-steroid-induced rise in GH concentration, and they suggest that the levels of GHBP may be related to the GH secretion and its variation with treatment.