A gentamicin-resistant isolate of Staphylococcus aureus producing staphylococcal enterotoxin F (SEF) was isolated from a burn unit nurse during three episodes of toxic-shock syndrome (TSS). The nurse's reciprocal titer of antibodies to SEF was less than or equal to 5 during the three episodes, and when the titer rose to 1,000 no further relapses occurred despite continued colonization. The unusual antibiotic susceptibility pattern of the organism enabled demonstration of its spread. During four months, 12 (41%) of 29 burn unit patients, three other burn unit nurses, and a household contact of the nurse with TSS became colonized. None, including two patients whose initial reciprocal titers were less than or equal to 5, developed TSS. This experience illustrates significant cross-transmission of a TSS-associated strain and a temporal association of antibodies to SEF with cessation of recurrences of TSS. Additional factors must explain why other individuals lacking antibodies to SEF did not develop TSS.