Hypothesis: The morbidity following treatment for perforated appendicitis in children is significant, with intraabdominal abscess being one of the more serious complications. This can lead to prolonged hospitalizations and antibiotic administration, multiple computed tomographic scans, and invasive procedures. The purpose of our study was to determine risk factors for developing an intra-abdominal abscess following treatment for perforated appendicitis. Design: Case-control study. Setting: Four tertiary care children's hospitals. Patients: Children aged 1 to 18 years with appendicitis. Intervention: Multivariable logistic regression. Main Outcome Measures: Development of postoperative abscess, length of hospital stay, presence or absence of fever, and tolerance of diet on postoperative day 3. Results: Thirty-five (13.2%) of 265 children developed an abscess. Ten factors with a bivariate P value <.20 were included in the regression model. The final multivariable model revealed only 2 factors influencing abscess development: an intraoperative fecalith (odds ratio, 8.77 [95% confidence interval, 1.50-51.40]) and diarrhea at presentation. Many factors proposed to be associated with abscess were not, including pain history, type and timing of preoperative antibiotics, abscess at operation, laparoscopic procedure, and length of antibiotics postoperatively. Thiry-seven children were discharged on or before postoperative day 3. Another 21 children were afebrile and tolerating a diet at that time but remained in the hospital. There were no significant differences between the 2 groups. None of the early-discharge group developed an abscess, and 2 of those remaining in the hospital developed an abscess (P=.06). Conclusions: Clinical factors commonly thought to be predictive of abscess formation following perforated appendicitis were not reliable predictors of this outcome. Our results suggest that if children are afebrile and eating on postoperative day 3 they can be discharged with a low rate of abscess development.