Group A streptococcus is an uncommon but important cause of nosocomial infections. Outbreaks of infection most often have occurred in surgical or obstetrical patients. We describe an outbreak of severe group A streptococcal infections that occurred on a medical unit of a community hospital. Within an 8-day period, three patients developed fatal nosocomial skin and soft-tissue infection due to group A streptococcus. Three nurses who had provided care to one or more of these patients subsequently developed streptococcal pharyngitis, and three other nurses were treated with antibiotics for pharyngitis (cultures not obtained). Patient isolates were serotype M-nontypeable, T-11, opacity factor-positive, and shared identical DNA profiles when typed by pulsed-field gel electrophoresis; staff isolates were not available for typing. To prevent further spread of infection, the ward was closed to new admissions, and symptomatic staff were treated with antibiotics and relieved of patient-care duties. This outbreak demonstrates the ability of group A streptococcus to spread rapidly in a hospital setting and to cause severe life threatening disease in hospitalized patients.