In the course of 1975 and 1976 the authors applied Partusisten (Th 1156 a) in 34 pregnant women at the risk of spontaneous abortion in the 16th to the 28th week of pregnancy. The therapy started with intravenous infusions by means of an automatic electromechanic infusion pump; peroral application of the drug followed, both in hospital and for a certain period in outpatient treatment under the gynecologist's supervision. Out of 34 women, 27 remained pregnant for more than 37 week of gestation and gave birth to a live at-term baby; in 5 cases the success was relative, and only in 2 cases was there no success at all. According to the tocolysis index, at index 2 or less, the success was achieved in 87% of cases and at index exceeding 2, the success was achieved in 63% of cases. The side-effect observed was invariably tachicardia in the mother, while all other untoward effects (tremor, sweating, slight restlessness, etc) were tolerated very well. An extremely good effect of Partusisten is obvious, because in doses of 4 micrograms/min, it promptly reduces the frequency and intensity of contractions.