This study evaluates the capacity of treatment with the combination of growth hormone (GH) and gonadotropin releasing hormone (GnRH) analog to preserve the height potential of 24 patients (15 girls, 9 boys) with GH deficiency and early puberty (onset at 7.8 +/- 0.5 SE yr in girls and 9.0 +/- 0.7 yr in boys). All but 4 were given cranial irradiation. They (group 1) were compared with 17 patients of normal pubertal age treated with GH for cranial irradiation-induced GH deficiency (group 2) and with 19 girls treated with GnRH analog for idiopathic central precocious puberty (group 3). The adult heights in groups 1, 2 and 3 were -0.5 +/- 0.2, -1.3 +/- 0.2, and -0.2 +/- 0.2 SD, significantly lower (P < 0.01) in group 2. They were lower than the target heights in groups 1 and 2 (P < 0.001), and similar in group 3. They were similar to the predicted heights at the onset of therapy (combined, GH, or GnRH analog therapy), except in group 3 (adult height > predicted height, P < 0.0001) In group 1, as in group 3, the differences between adult and predicted heights (1.1 +/- 1.3 and 6.5 +/- 1.4 cm respectively) correlated positively with the difference between bone and chronological ages (P < 0.05), negatively with the predicted height (P < 0.002), and positively with the difference between the target and predicted heights (P < 0.001) at the onset of therapy. In conclusion, treatment with the combination of GH and GnRH analog in patients with GH deficiency and early puberty leads to a normal adult height. This height is similar to the predicted height at the onset of therapy but lower than the target height.