We analyzed the final height of 146 short children with either nonacquired GH deficiency or idiopathic short stature. Our purpose was 1) to assess growth according to the pituitary magnetic resonance imaging findings in the 63 GH-treated children with GH deficiency and 2) to compare the growth of the GH-deficient patients with normal magnetic resonance imaging (n = 48) to that of 32 treated and 51 untreated children with idiopathic short stature (GH peak to provocative tests >10 microg/liter). The mean GH dose was 0.44 IU/kg.wk (0.15 mg/kg.wk), given for a mean duration of 4.6 yr. Among the GH-deficient children, 15 had hypothalamic-pituitary abnormalities (stalk agenesis), all with total GH deficiency (GH peak <5 microg/liter). They were significantly shorter and younger at the time of diagnosis than those with normal magnetic resonance imaging, had better catch-up growth (+2.7 +/- 0.9 vs. +1.3 +/- 0.8 SD score; P < 0.01), and reached greater final height (-1.1 +/- 1.0 vs. -1.7 +/- 1.0 SD score; P < 0.05). Among patients with normal magnetic resonance imaging, there was no difference in catch-up growth and final height between partial and total GH deficiencies. GH-deficient subjects with normal magnetic resonance imaging and treated and untreated patients with idiopathic short stature had comparable auxological characteristics, age at evaluation, and target height. Although they had different catch-up growth (+1.3 +/- 0.8, +0.9 +/- 0.6, and +0.7 +/- 0.9 SD score, respectively; P < 0.01, by ANOVA), these patients reached a similar final height (-1.7 +/- 1.0, -2.1 +/- 0.8, and -2.1 +/- 1.0 SD score, respectively; P = 0.13). Pituitary magnetic resonance imaging findings show the heterogeneity within the group of nonacquired GH deficiency and help to predict the response to GH treatment in these patients. The similarities in growth between the GH-deficient children with normal magnetic resonance imaging and those with idiopathic short stature suggest that the short stature in the former subjects is at least partly due to factors other than GH deficiency.