During a four-month period, ten cases of group A streptococcal (GAS) postoperative wound infection occurred among patients in a community hospital. Bacteremia developed in two patients, and one patient died. Group A streptococcal surgical wound infections were associated with exposure to a circulating nurse and duration of surgery. Prophylactic antibiotic reduced the risk of infection. Vaginal, perineal, and anal cultures from nurse A yielded GAS, serotype M-4, T-4, as did the blood of two infected patients. Penicillin eradicated GAS colonization of nurse A, and she returned to work. Five months later, two additional cases of GAS postoperative wound infections occurred and were associated with recolonization of the same nurse with GAS, serotype M-nontypeable, T-12. She was relieved of patient-care duties, and no further cases have occurred.