In this study, presence of some important pathogens such as Bovine Herpesvirus 1 (BHV-1), Bovine Viral Diarrhea Virus (BVDV), Campylobacter, Brucella and Mycoplasma were investigated by viral and bacteriological isolation, PCR/RT-PCR and serological methods in bulls. Seventy three semen, 94 preputial washings and 101 serum samples from bulls above 1 year old brought in slaughterhouse and, 210 extended semen samples collected in different dates from 19 bulls in an artificial insemination center and their sera were examined. BHV-1 and BVDV were not determined by PCR/RT-PCR and virus isolation in semen samples. Brucella and Campylobacter were not isolated in any of semen and preputial washing samples. Mycoplasma spp. was isolated in 24 (25.5%) of 94 preputial washing samples. In 120 bull sera (19 sera from an artificial insemination center, 101 from slaughterhouse) tested by ELISA, 42 (35 %) were positive for BHV-1 and 46 (39.6 %) for BVDV antibodies. Of the 19 bulls in an artificial insemination center all were seropositive for BHV-1 and 4 were seropositive for BVDV. All serum samples were negative for Brucella antibodies. None of the bulls examined in this study had any clinical symptoms.