Enterotoxin production by strains of Staphylococcus aureus isolated from routine samples of foods and from human beings was investigated. Twenty-one to 26% of 112 strains isolated from raw meat, sausages and poultry and 32–36% of 183 strains isolated from cooked foods, e.g. meat, chicken and frozen seafoods, produced enterotoxins A, B, C, D or E. Staph. aureus isolated from raw meat and chicken less frequently produced enterotoxins A, B, C or E and more frequently enterotoxin D, than those from cooked meat and seafoods. Of the 113 strains isolated from cheese and raw milk 6–11% produced enterotoxin and most of these produced enterotoxin D. Only a few strains isolated from foods produced enterotoxin E. Results of enterotoxin tests on Staph. aureus from human beings resembled those on strains from cooked foods.