Staphylococcus aureus is highly vulnerable to destruction by heat treatment and nearly all sanitizing agents. Thus, the presence of this bacterium or its enterotoxins in processed foods or on food processing equipment is generally an indication of poor sanitation. S. aureus can cause severe food poisoning. It has been identified as the causative agent in many food poisoning outbreaks and is probably responsible for even more cases in individuals and family groups than the records show. Foods are examined for the presence of S. aureus and/or its enterotoxins to confirm that S. aureus is the causative agent of foodborne illness, to determine whether a food is a potential source of "staph" food poisoning, and to demonstrate post-processing contamination, which is generally due to human contact or contaminated food-contact surfaces. Conclusions regarding the significance of S. aureus in foods should be made with circumspection. The presence of a large number of S. aureus organisms in a food may indicate poor handling or sanitation; however, it is not sufficient evidence to incriminate a food as the cause of food poisoning. The isolated S. aureus must be shown to produce enterotoxins. Conversely, small staphylococcal populations at the time of testing may be remnants of large populations that produced enterotoxins in sufficient quantity to cause food poisoning. Therefore, the analyst should consider all possibilities when analyzing a food for S. aureus.