Modern treatment for anovulatory infertility increases the incidence of multiple pregnancies with three or more fetuses and predisposes to prematurity with high perinatal mortality and mortidity. Premature labor was successfully treated in four multifetal pregnancies with ritodrine hydrochloride, a beta-mimetic drug relaxing the uterus. Another patient misdiagnosed as false labor was not treated and lost three out of four premature babies. Beta-mimetic treatment is indicated in multiple pregnancies even in false labor, or when painless progress in cervical dilatation is observed, to avoid asymptomatic progression into true labor. In contrast to singleton pregnancies, advanced labor with more than four centimeters cervical dilatation should not preclude good chances for successful treatment. Persistence in treatment and repreated use of the most effective intravenous route combined with oral ritodrine administration is needed because of marked tendency to recurrences of premature labor. Progressive increase in the dose of oral ritodrine may be indicated by decrease in therapeutic response. Maternal tachycardia should be considered as an index of patient responsiveness to the beta-mimetic treatment. The therapy is most successful when the patient is hospitalized from the first episode of treatment until at least the 37th week of pregnancy. This is probably less expensive than prolonged hospitalization of several prematures in an intensive care nursery.