This is a Program Project to further elucidate the hypothalamic control over gonadotropin and prolactin secretion. The Program Project is divided into six Projects which are the following: Project I consists of further studies on the production and action of LHRH; Project II consists of an evaluation of the role of brain peptides in control of gonadotropin and prolactin release; Project III is a study of monoaminergic, peptidergic and steroidal interactions in the hypothalamic control of LH and prolactin release; Project IV is a study of the neuroendocrinology of puberty and sexual development; Project V is an evaluation of the physiology and functional morphology of peptide neurons; and Project VI is an examination of the factors affecting hypothalamic secretion of LHRH. The Program Project is supported by three Cores which consist of a Radioimmunoassay Core I, Histology Core II and Administrative Core III. It is hoped that the results of these interdisciplinary studies will shed much further light on the operation of the hypothalamic pituitary unit which regulates secretion of gonadotropins and prolactin.