The objective of the studies was to determine the level of spermagglutinin in blood sera of cows of multiple ineffective inseminations. The studies were performed on 219 cows and 12 heifers of the black-and-white breed. The titre of spermagglutinins was checked by the use of the Deo and Roy the microagglutination test. The titre of agglutinins was defined as a lowest blood dilution in which agglutination could be recorded. In the present paper a positive results is titre of 1:32 or higher. Most sera have titres from 1:32 to 1:64. High titres were found (> 1:128) in cows of multiple inseminations (3 or more inseminations). The results obtained indicate a correlation between the titre of spermagglutinins in blood and the number of inseminations. Just after 3-4 ineffective inseminations antibodies against bull semen appear at titres that cause fertility disturbances (titres of 1:32 or higher). It is justified to demand that cows after 2 ineffective inseminations should be thoroughly examined for causes of infertility and they should be properly cured before another insemination is applied.