The efficacy of GH for increasing adult height (AH) in short adolescents born small for gestational age (SGA) is unclear, due to the lack of long-term controlled trials. A total of 168 short children born SGA (age, 10.5 yr for girls and 12.5 yr for boys) were randomly assigned to receive either 0.067 mg/kg.d GH until attainment of AH or no treatment. In this per-protocol analysis, 91 of 102 patients in the treated group and 33 of 47 patients in the control group were followed to AH. Mean height at inclusion was -3.2 SD score (SDS). Treatment duration was 2.7 +/- 0.6 yr. AH was -2.7 +/- 0.9 and -2.1 +/- 1.0 SDS in the control and treated groups, respectively (P < 0.005). The groups differed by 0.6 SDS units (95% confidence interval, 0.2-0.9). Height gain was 0.5 +/- 0.8 and 1.1 +/- 0.9 SDS in the control and treated groups, respectively (P = 0.002). Multivariate analyses confirmed the independent effects of treatment (0.6 SDS) and treatment duration (0.4 SDS/yr). All potential biases would tend to decrease the estimate of the treatment effect. Treatment tolerance was excellent. We concluded that the potential for spontaneous catch-up in short adolescents born SGA is limited. GH treatment increases AH by at least 0.6 SDS in this population.