Pathological and bacteriological studies were made of a total of 111 udders from slaughtered Korean native cows originating from various locations in Chonnam province. Incidence of supernumerary teats was 8.1%. Gross lesions were found in 21.4% of mucous membranes of total teat cisterns; these lesions comprised epithelial hyperplasia (12.6%), congestion (4.1%), slight fibrosis (3.8%) and severe fibrosis with congestion (0.9%). Gross lesions in the glandular tissues were found in 35.1% of cows; these lesions comprised slight fibrosis (27.9%), moderate fibrosis (6.3%) and severe fibrosis with pus (0.9%). Mastitis was found only in one cow. One hundred and twenty-five strains of microorganisms were isolated from mammary gland fragments of the cows. Pathogens most commonly isolated were Staphylococcus spp.; most of them were minor mammary pathogens. Major mammary pathogens were Streptococcus spp. (9.6%) and E. coli (2.4%). Most of the isolates were susceptible to many of 13 antimicrobial agents used, but Streptococcus spp. and Gram-negative rods showed resistance to 7 and 8 agents, respectively. 97.5% of the isolates showed susceptibility to amoxicillin, but only 55.8% to erythromycin.