Control Group: We have more than 20 previously studied children, 5.3 +/- 2.8 years of age, who have abnormal growth and have never received GH. All have undergone extensive auxologic, hormonal, neurocognitive and neuroimaging evaluations. These studies were done 15.4 +/- 9 months ago (range 11-28 months). We have already shown that, in the absence of intervention, height S.D. and pIQ are stable over time; therefore, these children can serve as their own controls.