The growth behavior of S. aureus in fresh cheese (Minas and Mozzarella) during their shelf life was studied in this research. The possibility of injury to this microorganism caused by increasing acidity was also investigated. Raw milk was inoculated with S. aureus FRIA-100 with approximately 10(6) cells/ml and cheese production was carried out according to normal procedures. They were stored at 7 degrees C during 40 days for Minas cheese and during 60 days for Mozzarella cheese. At 2 to 3 days intervals the following analyses were performed: acidity, pH, S. aureus count on Baird-Parker agar by traditional methods and by the method recommended by the American Public Health Association, to count repair of injured cells. We were certain of the presence of injured S. aureus when acidity was in the range of 0.7 to 0.8% expressed as lactic acid and when the count was 1.3 log higher.