Advances in perinatal and neonatal care in the past decade have produced a change in the population of infants with perforated necrotizing enterocolitis (NEC) treated at our institution: the majority are now of very low birth weight (VLBW, < 1,000 g). Peritoneal drainage has been reported as an initial resuscitative procedure for unstable infants who have complicated NEC. Initial success with peritoneal drainage prompted us to adopt an aggressive approach to its use in this patient population. Since 1987, peritoneal drainage has been the primary treatment for most infants weighing less than 1,500 g who have perforation, and for unstable infants weighing more than 1,500 g. Perforation was documented by pneumoperitoneum or aspiration of meconium by paracentesis. Intestinal resection was performed in most infants weighing more than 1,500 g and in those for whom drainage was ineffective. Twenty-nine infants with low or VLBW (mean gestational age, 27 weeks; mean birth weight, 994 g) were treated with one or two drains in the right lower quadrant. Broad spectrum antibiotics were continued until all drains were removed, usually within 10 to 14 days. Nasogastric suction was continued until patency of the gastrointestinal (GI) tract was confirmed by a nonionic upper GI series. Six (21%) infants died, although one of the deaths occurred 5 months after drainage; the patient had chronic lung disease and an intact GI tract. Seventeen of the 23 (74%) survivors required no further operative procedure, and 6 (26%) required laparotomy and resection because drainage had been ineffective. Peritoneal drainage provided definitive treatment in 18 of 29 (62%) infants in this series.(ABSTRACT TRUNCATED AT 250 WORDS)