In adults, persistent diffuse peritonitis (PDP) having a special microbiologic spectrum is now defined as a distinct intraabdominal infection because of its aggressive clinical course. Considering also other types of peritonitis, this study was performed to determine characteristics of childhood PDP in regard to clinical picture, microbiologic features, treatment and outcome. Classification of 175 patients with peritonitis showed that nine patients had primary peritonitis and 121, 37 and eight patients had secondary peritonitis, PDP, and intraabdominal abscess, respectively. Rates of host defense affecting disease, extra-appendicular origin, and mortality were markedly higher in the PDP group. However, polymicrobic and anaerobic infection rates were lower in the PDP group than those of the secondary peritonitis group. While 26 of 37 patients with PDP underwent surgical intervention, the remaining 11 patients were managed by conservative measures. In the PDP group, mortality was 18 percent for conservatively and 23 percent for surgically treated patients. Being of young age, presence of an accompanying disease and fungal growth increased the mortality. The results indicate that PDP is a distinct type of peritonitis in children as well as in adults. In addition, accurate identification of these patients may prevent some unnecessary operations and improve survival by the choice of more conservative treatment plans.