Dysmenorrhea, disfunctional uterine bleeding, preterm labor and postpartum labor in female mammals are treated by inhibiting uterine contractility by administering thereto a nitric oxide synthase substrate, a nitric oxide donor or both, optionally in combination with one or more of a prostaglandin inhibitor, a prostacyclin-mimetic, a progestin, an oxytocin antagonist or a β-agonist in an amount effective to ameliorate the symptoms thereof; and inadequate menses treated and induction of abortion or stimulation of labor in a pregnant female is achieved by uterine contractility stimulation by administering thereto a nitric oxide inhibitor, either alone or in a combination of progesterone antagonist, an oxytocin or oxytocin analogue antagonist or prostaglandin.