By means of a simple method for extraction of blood samples, reliable recoveries of vasopressin and oxytocin were obtained. This method was used in anaesthetized cats for estimation of these hormones, released into external jugular venous blood, after localized electrical stimulation in the hypothalamus. Stimulation of the supraoptic nucleus or supraoptico-hypophysial tract released large amounts of vasopressin without oxytocin. Stimulation of the paraventricular nucleus or tractus paraventricularis cinereus (Greving) released moderate amounts of vasopressin alone. Stimulation at points in the tuberal region of the hypothalamus released oxytocin with or without vasopressin. These could lie on the caudal tract from the paraventricular nucleus (Laqueur).