Background: The endoscopic resection of sinonasal inverted papillomas (IPs) has been well described. However, the majority of published reports in the literature are small case series with limited clinical follow-up. The aim of this retrospective study was to review the experience with the endoscopic and endoscopic-assisted resection of IPs at a major academic tertiary care facility and assess long-term outcomes. Methods: A retrospective review of endoscopic and endoscopic-assisted resections of IP was performed. Charts were reviewed for standard demographic data, operative technique, adjuvant approaches, complications, and postoperative follow-up times. Results: One hundred fourteen patients (average age, 56 years) underwent endoscopic or endoscopic-assisted resection for IPs with a mean disease-free follow-up of 40 months (7-135 months). Seventeen patients developed disease after endoscopic or endoscopic-assisted resection for a recurrence rate of 15%. Average time to recurrence was 23 months. Combined approaches were used when indicated in 34% (39/114) of patients, including adjuvant osteoplastic flap, midface degloving, trephine, or Caldwell-Luc approaches. Four patients (4%) had cerebrospinal fluid leaks that were successfully repaired endoscopically. Conclusion: In this large series of endoscopically resected IPs with extensive clinical follow-up, recurrences occurred an average of 23 months after the procedure. This emphasizes the importance of long-term endoscopic follow-up to detect recurrences in all patients. Endoscopic or endoscopic-assisted resection of IPs is a valid technique in this series with recurrence rates comparable with open approaches. Copyright © 2007, OceanSide Publications, Inc.