The production of toxic shock syndrome toxin 1 (TSST-1) by Staphylococcus aureus MN8 exposed to a range of oxygen concentrations (0 to 21% [vol/vol]) was examined in batch and thin-film cultures. The response of S. aureus to this range of oxygen concentrations was studied in the absence and in the presence of 7% (vol/vol) carbon dioxide. In the absence of carbon dioxide, TSST-1 production in batch cultures increased from negligible levels in the presence of oxygen concentrations of 1% or less to 500 ng/ml in the presence of 2% oxygen and then decreased to 70 ng/ml or less in the presence of oxygen concentrations of 6% and higher. In the presence of carbon dioxide, however, toxin production increased from negligible levels in the presence of 1% oxygen to 1,900 ng/ml in the presence of 21% oxygen. In thin-film cultures, TSST-1 production increased from nearly undetectable levels under anaerobic conditions to 1 and 10 microg/ml under 21% oxygen in the absence and presence of carbon dioxide, respectively. This study demonstrates the controlling effects of both oxygen and carbon dioxide on TSST-1 production.