Pituitary-hypothalamic abnormalities due to impaired cerebrospinal fluid circulation have long been recognized. The aim of this study was to assess pituitary, thyroid, adrenal, and gonadal function in 46 prepubertal (22 M and 24 F) and 10 pubertal (4 M and 6 F) subjects with myelomeningocele (MMC). Basal serum levels of FT3, FT4, TSH, PRL, LH, FSH, T or E2, cortisol, 17-OH-P and DHEA-S were measured by routine radio-immunoassay methods. Twenty-two prepubertal patients had a TRH test for TSH and PRL evaluation, and eight underwent a GnRH test. Three patients presented with precocious puberty. Six subjects had modest elevations of serum TSH together with normal free thyroid hormone levels. In three cases, TSH responses to TRH were significantly exaggerated and prolonged: in two patients, TSH responses were delayed. The mean basal plasma FSH level in females with ventriculo-peritoneal shunt was significantly higher than in controls. In six cases FSH responses to GnRH were significantly higher than in controls. Both basal and stimulated PRL levels were elevated in patients with shunts; in patients without shunts, basal PRL was normal, but peak PRL levels following TRH stimulation were elevated. Our data show an abnormal hypothalamic-pituitary function in MMC subjects. These findings reinforce the importance of physical examination, hormonal evaluation and follow-up of pubertal development in patients with myelomeningocele.