Inverted papilloma, a benign sinonasal lesion, constitutes 0.5% to 4% of all nasal tumors. Its local aggressiveness, high recurrence rate, association with malignancy or malignant transformation, and tendency toward multicentricity lead most physicians to advocate radical surgery. Nonetheless, conservative surgery is effective for selected patients with limited disease. This study was done to reassess the efficacy of both radical and conservative surgery.The records of all patients with the diagnosis of inverted papilloma treated at the Taipei Veterans General Hospital between January 1986 and October 1998 were collected. A minimal follow-up period of 12 months was required for inclusion in the study. Clinical manifestations, radiologic findings, methods of treatment, pathology reports and recurrence rates were all retrospectively reviewed.Sixty patients with an average age at diagnosis of 58 years were studied. The follow-up period ranged from 12 to 195 months, with a mean of 43 months. The most common presenting symptom was unilateral nasal obstruction. The duration of symptoms ranged from one month to 30 years, with a mean of 36 months. The lateral wall and middle meatus were the most commonly involved sites. Bone erosion and intracranial or intraorbital extension were observed in some patients. Medial maxillectomy was the most common surgical treatment, followed by functional endoscopic sinus surgery and the Caldwell-Luc operation. The overall recurrence rate was 23%, with an average interval from initial treatment to recurrence of 42 months (range, 2-93 months). The recurrence rates for the two groups undergoing medial maxillectomy and conservative surgery were 16% and 27%, respectively.Early diagnosis relies on high suspicion and biopsy. The treatment modality is related to the location and extent of the disease, which is assessed by preoperative imaging studies. Any tumor with extensive involvement of the sinuses or inaccessibility to the endoscope should be treated with traditional medial maxillectomy for best control. The endoscopic technique is good for preoperative biopsy and follow-up.