In patients with allergic fungal sinusitis, the mainstay of treatment remains surgical removal of allergic mucin and fungal debris. But as a single modality, surgery is associated with high rates of recurrence, so a number of adjunctive medical modalities have been tried, including postoperative corticosteroid therapy. We conducted a study of 63 patients with allergic fungal sinusitis who underwent endoscopic sinus surgery with or without postoperative steroid therapy. A group of 30 patients who had been treated prior to January 2000 had undergone surgery only; their cases were reviewed retrospectively, and they served as historical controls. Another 33 patients who were treated after June 2000 underwent surgery plus oral and nasal steroid therapy. All patients were followed for a minimum of 2 years. Recurrences were seen in 50.0% (15/30) of the no-steroid group and 15.2% (5/33) of the steroid group-a statistically significant difference (p = 0.008). The results of our study strongly support the use of steroids to control allergic fungal sinusitis and prevent its recurrence, and we recommend further study to identify the optimal dosage and duration of therapy.