RESUMEN
During a period of artificial insemination in cattle in several farms around Tehran, Iran, the animals were involved with endometritis and abortion. In order to investigate the cause, bacterial culture was done on 23 samples of artificial prepared semen. Haemophilus sp. was isolated from 20 out of 23 samples and the findings were confirmed through serologic tests. Biochemical tests were also set up to diagnose the strain of the bacteria. These tests revealed the presence of H. somnus in the artificially prepared semen. This species was never before reported in Iran, in genital tract of cattle [male and female] nor H. agni in sheep. Attempts to culture this bacteria from genital tract has not been very successful because of cultural difficulties. This was the first diagnosis of H. somnus in this country and helped the practitioners to be aware of the possible problems in running the artificial insemination procedure from infected semen