We describe the case of a short-statured 12-yr-old boy who developed a Chiari type 1 malformation associated with central sleep apnea after administration of high-dose GH therapy, which he had been receiving since the age of 10 yr and 4 mo. He responded well to GH therapy, and his height increased by 18.8 cm in 2 yr. At 12 yr and 4 mo of age, his mother reported that he had developed sleep apnea during the previous year and it had worsened over a month prior to presentation at our hospital. Otolaryngological examination did not reveal tonsillar or adenoidal hypertrophy. Polysomnography demonstrated severe central sleep apnea with an apnea-hypopnea index of 46.5/h. Sagittal T1-weighted magnetic resonance imaging (MRI) demonstrated herniation of the cerebellar tonsils 15 mm below the foramen magnum into the cervical spinal cord. Continuous positive airway pressure therapy initiated prior to performing neurosurgery was ineffective. Following uncomplicated foramen magnum decompression, his breathing pattern during sleep returned to normal. Sagittal MRI examination should be considered in patients who develop sleep apnea during/following administration of GH therapy.