Objective: To determine the efficacy of endoscopic surgery for chronic frontal sinusitis. Design: A prospective analysis of established measures of clinical outcome (Chronic Sinusitis Survey and Short Form 36) that was administered to patients before frontal sinus surgery and at intervals of 3 months, 6 months, and 1 year after surgery. Interventions: For limited disease, the frontal recess was opened and the frontal ostium probed or enlarged. For more severe cases, a drill was used to resect the frontal sinus floor and interfrontal septum. Setting: Private and institutional-based practices at an academic medical center. Subjects: Eighty-seven patients who underwent endoscopic surgery for frontal sinusitis, including 24 patients with severe disease who underwent a frontal sinus drillout procedure. Main Outcome Measures: Scores on the Chronic Sinusitis Survey, Short Form 36, and surgical revision rate. Results: Significant improvement in facial pain, nasal drainage, and congestion was observed 1 year after surgery (P<.01). Medication use was also significantly reduced during this period (P<.01). Quality-of-life measures showed greatest improvement in the domain of social functioning (P<.05). Three (12.5%) of 24 patients who underwent a frontal sinus drillout procedure did not respond to surgery secondary to restenosis Of the Frontal ostium. Conclusions: Although the long-term results of endoscopic surgery for frontal sinusitis are unknown, this approach appears to be effective for most patients and may provide a reasonable alternative to frontal sinus obliteration surgery in selected cases.