Intracellular records were obtained from paraventricular neurones injected with Lucifer Yellow in slices from the rat hypothalamus. Slices containing fluorescent neurones were then serially cut and alternating sections were stained immunocytochemically for vasopressin or oxytocin. Double-labelled cells were found which fluoresced and which had reacted with either vasopressin or oxytocin antiserum.