This paper describes a rapid sensitive solid phase radioimmunoassay procedure for staphylococcal enterotoxin B, which can be applied to A and C. The procedure is 100-fold more sensitive thandescribed immunodiffusion and precipitin methods and is reliable at a level of 0.01 µg/ml. It is usable for detection ad measurement of enterotoxin in foodstuffs, biologic fluids and toxin preparations, both purified and crude.