Staphylococcus aureus and group A Streptococcus pyogenes produce toxic shock syndrome characterized by hypotension and multisystem organ failure. While conventional therapy has consisted of antibiotics and intensive supportive care, some experimental evidence suggests that immunoglobulins directed against the toxins may be effective additional therapy. We report a case of "toxic strep syndrome" in which intravenous immunoglobulin was administered when signs and symptoms were worsening while the patient was receiving conventional therapy. Within hours of administration of the intravenous immunoglobulin, the patient experienced dramatic clinical improvement. This response suggests a possible therapeutic benefit of intravenous immunoglobulin in toxic shock syndrome.