Modern β-receptor agonists are potent inhibitors of uterine activity, both spontaneous and induced, and there are several indications for therapy, such as preterm labor, abnormal uterine activity during labor (with or without concomitant fetal distress), complicated cesarean sections, and others. In recent years the widespread use of β-receptor agonists for preterm labor has been criticized and the efficacy of these drugs has been questioned, since the rate of preterm deliveries (before week 37) has remained unchanged. However, an analysis of preterm births in Sweden from 1973 to 1979 shows that the number of both preterm births before week 32 and of infants with birthweight below 1 500 g is declining, which is more interesting in terms of fetal outcome than is the crude preterm figure (before week 37). The introduction of routine use of β-receptor agonists for preterm labor coincides with this decrease. It is concluded that these drugs can be of great value in many obstetrical situations.