An appreciable fraction of carbohydrate-negative (car) mutants of Staphylococcus aureus strains ATCC 14458, 778, and S-6 exhibit increased enterotoxin B (SEB) production. In addition, some lac and mtl mutants of these strains also display enhanced SEB formation. All such mutants appear to be point mutations. Mutagen-induced reversions of high SEB producing car, mtl, or lac mutants yield varying amounts of SEB and some clones seem to be restored to the characteristics of the parent type. A few sequentially isolated lac, mtl double mutants of strain 778 elaborate much more or much less SEB than either the lac or the mtl single mutants.