Effects of the electrical stimulation of the mammary nerve on oxytocin (OT) and luteinizing hormone (LH) secretion in anesthetized lactating rats were examined. The electrical stimulation of the mammary nerve as well as the saphenous and the median nerve increased the plasma OT concentration in both lactating and cycling rats under urethane anesthesia. All groups of rats stimulated with these nerves showed a very similar pattern of OT release which was different from those observed in lactating rats suckled by pups. The electrical stimulation of the mammary nerve decreased the plasma LH concentration in ovariectomized lactating rats that had been deprived of their pups for 24 hr compared with the concentration obtained after the stimulation of the saphenous nerve. The possibility still remains that the electrical stimulation of the mammary nerve could be used as a substitute for the suckling stimulus.