Investigations were performed to avoid cross‐reactions in the enzyme linked immunosorbent assay, using the sandwich technique, for detection of Staphylococcus aureus enterotoxin type B. Non‐specific reactions can be caused by cross‐reacting antigens and by Protein A, produced by S. aureus. The former reactions can be prevented by adsorption with culture filtrate of non‐toxin type B producing strains. The latter reaction is caused by the binding of Protein A to the Fc fragments of the IgG antibodies. Interference by Protein A was completely eliminated by using the F(ab')2fragments of the IgG antibodies.ELISA experiments in which these purified F(ab')2fragments were used resulted in a highly specific detection of entertoxin type B, both in culture filtrates and i