A total of 276 Staphylococcus aureus strains isolated from routine sampling, food poisoning outbreaks, and mastitic milk were examined for production of enterotoxins A, B, C, D, and E. Quantitative determination of thermonuclease was carried out from the dialysis sac culture supernatant fluids obtained during the enterotoxin assay. The toxic properties of the strains were compared with other biochemical properties (coagulase, phosphate, production of pigment, and hemotoxin) and with their sensitivity to antibiotics and phages. Fifty one percent of the strains examined produced enterotoxin, and of the toxigenic strains 53% produced enterotoxin A, 4% produced B, 38% C, and 20% D. Production of enterotoxin E was not observed with any of the strains. Production of thermonuclease averaged 19.4 and 25.5 μg/ml for toxigenic and non-toxigenic strains, respectively. All toxigenic strains produced coagulase, 98% produced phosphatase, 92% hemotoxin, and 79% yellow or orange pigment. Of the toxigenic strains isolated from food, 56% belonged to phage group III, and of the toxigenic strains isolated from mastitis cases 31.4% belonged to phage group M and 21% to phage group III. Resistance to antibiotics was slightly more widespread among the toxigenic than the non-toxigenic strains.