Context: Gonadotropin-releasing hormone analogues (GnRHa) and recombinant human growth hormone (rhGH) have been widely used to treat idiopathic central precocious puberty (CPP) or early and fast puberty (EFP). However, large-scale studies to evaluate the treatment effects on final adult height (FAH) are still lacking. Objective: To assess the effects of long-term treatment for CPP/EFP on FAH and its main influencing factors. Design and Setting: Retrospective, multicenter observational study from 1998 to 2017. Participants: Four hundred forty-eight Chinese girls with CPP/EFP received GnRHa and rhGH treatment (n = 118), GnRHa alone (n = 276), or no treatment (n = 54). Main Outcome Measures: FAH, target height (Tht), and predictive adult height (PAH). Results: The height gain (FAH-PAH) was significantly different among the GnRHa and rhGH treatment, GnRHa alone, and no treatment groups (P < 0.05; 9.51 +/- 0.53, 8.07 +/- 0.37, and 6.44 +/- 0.91 cm, respectively). The genetic height gain (FAH-Tht) was 4.0 +/- 0.5 cm for the GnRHa + rhGH group and 2.0 +/- 0.27 cm for the GnRHa group, while the control group reached their Tht. In addition, 5 critical parameters derived from PAH, bone age, and Tht, showed excellent performance in predicting which patients could gain >= 5 cm (FAH-PAH), and this was further validated using an independent study. Conclusions: The overall beneficial effect of GnRHa + rhGH or GnRHa on FAH was significant. The control group also reached their genetic target height. Clinicians are recommended to consider both the potential gains in height and the cost of medication.