BACKGROUND Video-assisted thoracoscopic debridement (VATD) is a new method of managing pediatric empyema. The purpose of this retrospective study was to determine the relation between the timing of VATD and its success in avoiding the need for open decortication. METHODS Twenty-one children aged 3 to 16 years (mean, 8 years) with symptomatic, loculated, parapneumonic empyema were treated with VATD at two tertiary pediatric centers between 1994 and 1997. The preoperative duration of symptoms, hospitalization, and previous need for thoracostomy drainage were compared between patients having VATD only and those who subsequently required a thoracotomy and decortication. Statistical analysis used the Wald chi-square test or Fisher's exact test with p < 0.05 considered significant. RESULTS Video-assisted thoracoscopic debridement was successful in 15 patients (group 1) and unsuccessful in six patients (group 2), who required a thoracotomy and decortication. Group 1 had a shorter mean duration of preoperative symptoms (13 versus 27 days; p=0.03), a shorter median duration of preoperative hospitalization (6 versus 18 days; p=0.04), and a lower incidence of previous thoracostomy drainage (4/15 versus 5/6; p=0.05). CONCLUSIONS The technique of VATD is most likely to be successful when used within one week of diagnosis of a loculated parapneumonic empyema. A prospective trial comparing VATD with intrapleural fibrinolytic agents for the initial treatment of pediatric empyema is needed.