Oxytocin (OT) is a member of the neurohypophyseal hormone family. OT receptors are found in uterine smooth muscle, myoepithelial cells in the mammary gland, and in the pituitary. OT stimulates contraction of uterine smooth muscle during labor and stimulates milk secretion in response to suckling. It has been postulated that OT may also facilitate social and bonding behaviors related to the reproduction and care of offspring. Further studies of the OT receptor are essential in gaining a better understanding of the mechanism and in vivo regulation of uterine function.