Streptococcal toxic shock syndrome (strepTSS) has been associated with various streptococcal soft-tissue infections including cellulitis, necrotizing fasciitis, and peritonitis in adults. We describe a 40-year-old patient with pharyngitis and strepTSS. Throat swab cultures yielded a strain of Streptococcus pyogenes that produced large amounts of erythrogenic toxin A. Fluorescence-activated cell sorter analysis of the patient's peripheral blood lymphocytes revealed generally enhanced expression of the T cell activity markers CD25 and human leukocyte antigen-DR and a marked increase in the number of gamma delta T cells, largely of the V delta 1-bearing subpopulation. Two more analyses, which were performed 2 weeks and 9 months later, respectively, documented the course of normalization after the acute episode of strepTSS. The T cells of this patient were stimulated in vitro with supernatants of his streptococcal isolate, and they proliferated in a dose-dependent manner. These proliferating T cells were mainly alpha beta T cells.