A total of 108 cows were gynecologically investigated. Twenty-four of them were found to be suitable as donors. These were within the range of the 40th to the 60th day following calving, were not inseminated, and had no complications at calving and over the puerperal period. Estrus was synchronized via implants (3 mg norgestomet Synchromate B, Intervet in s/c application); 8 days later the donors were injected with 3000 IU PMSG each in order to induce superovulation. On the 10th day the implants were removed, and each animal was injected with 22 mg prostaglandin F3 alpha. At the 24th hour following the onset of estrus half of the donors were injected with anti-PMSG (i/v). It was found that the capacity of cows to respond with superovulation after hormonal treatment was quite individual. The application of antigonadotropic sera on the first day of estrus limited superovulation and raised the number of fertilized ova, resp., of embryos able to be transplanted. It was demonstrated also that to shorten the period from washing the uterus up to the impregnation of the donor animals it is necessary to apply hormonal therapy and preventive measures in dependence on the functional and morphologic state of the ovaries and the sexual apparatus.