• In a review of 22 years of clinical experience, we found seven previously healthy children with primary peritonitis. The diagnosis was made at laparotomy in all patients. Their symptoms included diffuse abdominal pain, fever, vomiting, and diarrhea. Abdominal tenderness was maximal in the right lower quadrant in five children, which led to confusion with the diagnosis of acute appendicitis. Streptococcus pneumoniae was identified as the etiologic agent in three patients and group A β-hemolytic Streptococcus in one patient. The remaining three patients all had prior antibiotic therapy, and peritoneal fluid cultures were sterile. All children had a prompt response to treatment with antibiotics and recovered without complications. Long-term follow-up (4½ to 15 years) was available for three patients; all three remained healthy.