OBJECTIVE: Chronic isolated frontal sinusitis occurs infrequently. In this condition, most of the ethmoid cells are well aerated and the frontal sinus is involved secondary to anatomical obstruction or inflammatory changes confined to the frontal recess. The purpose of this study was to evaluate a targeted endoscopic technique where standard anterior ethmoidectomy is unnecessary in the treatment of chronic isolated frontal sinusitis. STUDY DESIGN AND SETTING: This retrospective study was conducted in a large university-affiliated hospital and included 11 patients with chronic isolated frontal sinusitis who underwent endoscopic sinus surgery limited to the frontal sinus outflow. The ethmoid bulla was untouched in all cases. Follow-up continued for 19 to 40 months (mean 28.6 months). RESULTS: Frontal sinus outflow patency was verified in 9 patients (81.8%). Nine patients, including one with an apparent nonpatent frontal ostium, reported improvement. Two patients-one of whom had a patent frontal ostium-reported no improvement. There were no complications. CONCLUSION: Chronic isolated frontal sinusitis can be effectively treated in selected cases by a targeted endoscopic procedure, limited to reestablishment of frontal sinus outflow. EBM rating: C-4.