It is now firmly established that LH-RH and its agonists can have direct inhibitory effects on gonadal function in male and female animals. The initial reaction to such findings was one of incredulity because they challenged one of the accepted 'truths' of endocrinology, namely that LH-RH was secreted only by hypothalamic neurones and acted only on the anterior pituitary. However, LH-RH, like other hypothalamic peptides (e.g. thyrotrophin-releasing hormone, somatostatin), is quite widely distributed throughout the body. Current evidence suggests that LH-RH-like peptides occur in spinal ganglia in the frog (Jan, Jan & Kuffler, 1979; Jan, Jan & Brownfield, 1980) and, in mammals, in the pineal gland (Wheaton, 1980), pancreas (Seppala, Wahlstrom & Leppaluoto, 1979; Wahlstrom & Seppala, 1979; Seppala & Wahlstrom, 1980a), certain human mammary tumours (Seppala & Wahlstrom, 1980b), the placenta (e.g. Khodr & Siler-Khodr, 1980; Lee, Seppala & Chard, 1981), ovary (Ying, Ling, Bohlen & Guillemin, 1981) and