Staphylococcus aureus is a major causative pathogen of clinical and subclinical mastitis of dairy domesticruminants. This agent produces a variety of extracellular toxins and virulence factors including Toxic ShockSyndrome Toxin-1 (TSST-1) which is the major cause of Toxic Shock Syndrome (TSS). In this study 58S. aureus isolates obtained from 9 dairy herds in East and West Azerbaijan provinces of Iran. The testedisolates were identified on the basis of the cultural and biochemical properties as well as by amplification ofthe aroA gene, specific to S. aureus. Isolates were also analyzed for the presence of the TSST-1 encodinggene (tst) using Polymerase Chain Reaction (PCR). tst gene 350 bp was detected in 9 (15.5%) of the totalnumber of 58 isolates. The present study revealed that the PCR amplification of the aroA gene could beused as a powerful tool for identification of S. aureus from the cases of bovine mastitis. Results also showedthat the strain of S. aureus which caused mastitis can potentially produce staphylococcal toxic shocksyndrome toxin-1. Overall, our results suggest that it is of special importance to follow the presence ofTSST-1 producing S. aureus in foodstuffs, especially for protecting the consumers from toxic shocksyndrome.