Eleven patients, ranging in age from 3 weeks to 17 years, had acute necrotizing fasciitis. Seven patients developed infection following surgery or trauma. The trunk was the most common site of involvement. Five patients had infection caused by group A β-hemolytic streptococci. Staphylococci, gramnegative organisms, or a mixture of bacteria caused the remainder. Cultures of the involved areas were positive in the ten cases in which specimens were obtained, and blood cultures were positive in eight of ten patients. Extension of infection to underlying muscle occurred in seven cases, and fasciotomy was performed in nine patients. Four patients died and five required skin grafting. Effective therapy must include fasciotomy and extensive debridement in addition to antibiotic administration.