The effect of PGF2alpha to induce parturition in sows was studied in two herds. In one herd with a total number of 150 sows and with a good health status 12 sows were injected intramuscularly with 12.5 mg PGF2alpha during late pregnancy (110--114 days). During the same period 12 sows were treated intramuscularly with saline solution at corresponding gestation stage. The results are given in Tables I and II. The mean age calculated as number of litters was 2.6 in the experimental group and 4.3 in the control group. All sows treated with PGF2alpha farrowed within 30 hours after injection at an average time of 25.4 hours. The controls farrowed at an average 80.2 hours after injection. The mean farrowing time was 4.4 hours for the PG-treated sows while the corresponding figure for the controls was 6.6 hours. The litter size at birth, after 3 weeks and at weaning was somewhat higher in the experimental group. The same applies to the litter weight at the age of 3 weeks. The course of parturition was normal in all sows and the health condition during lactation was good. In another herd -- numbering 18 sows -- all sows which hade farrowed during the last 4 months before the present investigation, had developed the Mastitis-Metritis-Agalactia syndrome (MMA). The symptoms were a prolonged gestation length (116--117 days), fever, mastitis and agalactia. During the present study 3 sows were left untreated while 5 sows were given an intramuscular injection with 12.5 mg PGF2alpha during late pregnancy (112--114 days). Four of the five PG-treated sows farrowed within 32 hours, while the fifth sow farrowed 100 hours after injection. The sow not responding to the PG-treatment and the untreated sows all developed MMA while the four sows responding to treatment remained healthy. The gestation length in treated sows responding to treatment was 113--115 days. In the sows developing MMA the gestation length was 116--117 days. The potential effect for prevention of MMA of shortening the gestation length in this herd is discussed.