On clinical grounds, arachnoid cysts are usually associated with neurological dysfunction. Little is known concerning their involvement in endocrine disorders. A seven-year-old boy was admitted to the hospital for evaluation of an unprovoked afebrile seizure. His neurological examination was normal, however, he had growth retardation. Insulin tolerance and L-dopa growth hormone stimulation tests revealed an inefficient growth hormone response. An MRI of hypophysis and cranium yielded a shift of hypophysis and a large arachnoid cyst.