The sows which had not returned estrus since 15 to 152 days after weaning were treated with PMSG or PGF2$\alpha$ to induce estrus and inseminated to conceive on that estrus. 1. Eight (83%) among 12 sows treated with PMSG came into estrus on average 5.3 days after treatment. 2. The one sow which didn't show any estrus by treatment of PMSG showed an estrus by intramuscular use of 10mg PGF2$\alpha$ and the other one showed an estrus by another intramuscular use of 1000 I.U. of PMSG at 15 days after first injection of PMSG. 3. The one sow injected with Vit. A.D.E. complex(Injacom) (Vit. A 500,000 I.U., Vit. D. 75,000 I.U., and Vit. E. 50 I.U. per ml) on 6 days before PMSG injection showed an estrus on 6 days after PMSG injection and farrowed 8 piglets. 4. Five among 10 sows showed an estrus by treatment of PMSG or PGF2$\alpha$ were pregnant and litter size of the four farrowed sows averaged 9.5.