Studied was the occurrence of enzootic bovine leukosis as dependent on the use of semen of leukosis-affected bulls for the artificial insemination of cows and heifers and their offsprings in the F1 generation on 16 farms. Semen was used of a total of 30 bulls of the Holstein-Friesian, American Brown, and European Black-and-white breeds. The agar gel immuno-diffusion test was employed to establish antibodies to the bovine leukosis virus in the sera of the bulls. On 9 farms with 2,997 cows and heifers that were negative for leukosis antibodies a total of 800 female calves (F1) were born. Serologic investigations of both dams and calves, aged 2 to 5 years revealed no leukosis antibodies. On other 7 farms with 1,717 cows and heifers, among which sporadic carriers of BLV-antibodies were discovered, 713 female offsprings (F1) were born. Seventeen (2.38 per cent) out of these responded positively for BLV antibodies. Twenty-two (3.0 percent) of the dams following calving also showed a positive reaction. Over the 1981-1985 period a total of 1,593 female calves were born as the offsprings of 4,714 cattle on all 16 farms. The percent of the positively responding to leukosis was 1.06, resp., 1.38. These results were considered indicative in ruling out the transmission of enzootic bovine leukosis with semen in the artificial insemination of cows and their F1 offsprings.