Causative agents of mastitis were isolated from glandular tissues of 101 culled Holstein cow udders and tested with antimicrobials by standardized disc diffusion method. Pathogens most commonly isolated were coagulase-negative staphylococci (43.9%) and streptococci (21.4%). Most of the udders (88.5%) showed mixed infections with more than two species of bacteria. Antimicrobial sensitivity tests revealed that 90.0% and 84.5% of the isolated organisms were susceptible to amoxicillin and gentamicin, while most organisms were resistant to erythromycin. Coliforms were resistant to ampicillin, cephalothin, cefazolin, erythromycin, kanamycin, neomycin, penicillin and tetracycline and streptococci to erythromycin, kanamycin, neomycin, trimethoprim/sulfamethoxazole and tetracycline.