Neurophysin and the octapeptide hormones oxytocin and vasopressin are synthesized in the hypothalamus and stored in the posterior lobe of the pituitary gland. It has recently been shown that the release of both oxytocin and vasopressin or of vasopressin alone, in response to potent stimuli, is accompanied by a simultaneous release of neurophysin into the circulation (Burton, Forsling & Martin, 1971; McNeilly, Legros & Forsling, 1972). However, it has yet to be shown that neurophysin can be released at the same time as a specific release of oxytocin. This situation occurs in animals during both parturition (Folley & Knaggs, 1965) and lactation (Folley & Knaggs, 1966; McNeilly, 1972). The present report describes the simultaneous release of oxytocin and neurophysin during parturition in the goat. Serial blood samples (approx. 10 ml each) were taken from an indwelling jugular cannula during the whole of labour in two pedigree British Saanen goats. Samples