Background. Inflammatory pseudotumors of the lung are rare and often present a dilemma for the surgeon at time of operation. We reviewed our experience with patients who have this unusual pathology. Methods. Between February 1946 and September 1993, 56,400 general thoracic surgical procedures were performed at the Mayo Clinic. Twenty-three patients (0.04%) had resection of an inflammatory pseudotumor of the lung. There were 12 women and 11 men. Median age was 47 years (range, 5 to 77 years). Six patients (26%) were less than 18 years old. All pathologic specimens were re-reviewed, and the diagnosis of inflammatory pseudotumor was confirmed. Eighteen patients (78%) were symptomatic which included cough in 12, weight loss in 4, fever in 4, and fatigue in 4. Four patients had prior incomplete resections performed elsewhere and underwent re-resection because of growth of residual pseudotumor. Wedge excision was performed in 7 patients, lobectomy in 6, pneumonectomy in 6, chest wall resection in 2, segmentectomy in 1, and bilobectomy in 1. Complete resection was accomplished in 18 patients (78%). Median tumor size was 4.0 cm (range, 1 to 15 cm). There were no operative deaths. Follow-up was complete in all patients and ranged from 3 to 27 years (median, 9 years). Results. Overall 5-year survival was 91%. Nineteen patients are currently alive. Cause of death in the remaining 4 patients was unrelated to pseudotumor. The pseudotumor recurred in 3 of the 5 patients who had incomplete resection; 2 have had subsequent complete excision with no evidence of recurrence 8 and 9 years later. Conclusions. We conclude that inflammatory pseudotumors of the lung are rare. They often occur in children, can grow to a large size, and are often locally invasive, requiring significant pulmonary resection. Complete resection, when possible, is safe and leads to excellent survival. Pseudotumors, which recur, should be re-resected.