This study determined the incidence, clinical characteristics, treatment and outcome in extremely low birth-weight (ELBW) premature infants with perforated necrotizing enterocolitis (NEC). We retrospectively reviewed the medical records of ELBW (birth weight <1000 g ) premature infants with perforated NEC diagnosed and managed at National Taiwan University Hospital (NTUH) from January 1993 through December 2000. A total of 8 ELBW premature infants with perforated NEC were collected. The incidence of perforated NEC in ELBW premature infants was 5.1% (8 out of 158). The average age at onset of perforated NEC was 26 days. The most common clinical features were abdominal distention, decreased bowel sound and poor activity level. Dilated and fixed bowel loops, bowel wall thickening and ascites with stool-like substance drainage out from penrose drain tube were the predominant signs at the time of diagnosis of perforated NEC. Thrombocytopenia, elevated C-reactive protein and anemia were the major laboratory findings. All infants received a primary penrose drain in the acute stage of disease. The overall survival rate was 37.5% (3 out of 8). Death occurred due to nosocomial infection with sepsis in 3 patients and due to perforated NEC in 2 patients. Two of the three surviving patients started enteral feeding 19 and 41 days after the diagnosis of perforated NEC and tolerated oral feedings well; the third patient still required total parenteral nutrition two years after diagnosis. Although the clinical characteristics and radiographic findings of perforated NEC in ELBW premature infants were variable, brown color ascites with stool-like substance may be considered a significant sign of perforated NEC despite the absence of free air on radiography at the early stage of disease. Close observation of clinical symptoms and signs, more aggressive surgical intervention and prevention of the following nosocomial infection may have the opportunity to reduce the mortality due to perforated NEC.