Population diversity was evaluated in strains of Staphylococcus aureus isolated from bovine mastitis in Brazilian dairy herds by PCR-RFLP and sequencing of the 3′-terminal portion of the coagulase gene, and the susceptibility of strains to antimicrobials. The results showed great diversity in S. aureus population studied and the existence of predominant clones that account for most infections. No associations between the predominant types observed in the PCR-RFLP and the forms of presentation of the mastitis or to any of the different patterns of antimicrobial resistance were observed.