Magnetic resonance imaging was performed using a 1.5 Tesla magnet in 22 children (14 boys and 8 girls) between 5-20 yr of age with isolated GH deficiency (IGHD), born by normal vaginal delivery without any birth asphyxia or trauma. A total of 22 children (10 boys and 12 girls) without short stature and endocrine disease were evaluated as controls. The IGHD group had a height velocity less than 4 cm/yr and delayed bone age. The peak GH levels were less than 10 micrograms/L (mean, 2.4 micrograms/L). The height of the pituitary gland ranged from 3-7.5 mm in controls. An intact stalk was observed in 21 children with IGHD, with nonvisualization in 1. An apparently thin stalk was seen in 6. The posterior lobe identified by the hyperintensity signal, had a mean diameter of 1.84 mm and was located in a normal position in 21 children. An ectopic posterior pituitary hyperintensity was present in 1 patient. The anterior pituitary was hypoplastic in 17 children, with partial empty sella in 13. A total of 5 children had associated brain anomalies, such as Arnold Chiari malformation, craniovertebral malformation with basilar impression, degenerative plaques around posterior horn of lateral ventricle and parietal area, and infarcts in caudate nucleus and putamen. These findings suggest that IGHD was not related to transection or compression of the stalk.