Staphylococcus aureus (S. aureus) is one of the infectious agents that induce severe mastitis in cows with a difficult bacteriological cure and high antimicrobial resistance. Because the microbiological culture of clinical samples only shows results in 50% of the cases (Koskinen et al., 2009), diagnostic through PCR is an alternative. The aim of this study was to prove if the primers described by Cremonesi et al. (2006) for the S. aureus diagnosis, with good sensitivity and specificity, could be used in clinical samples too. The results showed that the following nucleotide sequences can be used as primers: F 5' AGC TGT GGA TTG TCC TTT GG 3' and R 5' TCG CTC GCT CAC CTT AGA A 3' in order to obtain a 499 pb enlargemenr are not useful in clinical samples due their low specificity (62.95%). It is required to search new primers to amplify S. aureus regions not shared with other bacteria, especially those cauding mastitis in dairy cows.