OBJECTIVE To review the safety and efficacy of endoscopic drainage of subperiosteal orbital abscesses (SPOAs) secondary to sinusitis and to evaluate risk factors that may be associated with failure. METHODS Retrospective chart review. METHODS All patients admitted to the University of the Virginia Health System with a diagnosis of SPOA between 1992 and 1999 were reviewed. RESULTS Seven of the 10 SPOAs identified, each located medially, resolved without complication after endoscopic drainage. The remaining three patients required a second drainage. One patient had an inferiorly located SPOA, which recurred laterally after endoscopic drainage. A second pediatric patient, who did not undergo a routine second-look procedure, developed middle turbinate lateralization and synechiae, which led to recurrent SPOAs. A third patient with a significant history of sinusitis was found to have an ethmoid sinus mucocele extending into the medial and posterior orbit. All patients eventually resolved their symptoms. CONCLUSIONS Endoscopic drainage of medial SPOAs appears to be safe and effective. However, several risk factors must be recognized when present. Management of these risk factors is discussed.