Ostial obstruction is a major factor in the pathogenesis of sinusitis. Detailed diagnostic evaluation in patients with maxillary sinusitis demonstrates the prominence of disease in the ethmoidal infundibulum and in adjacent ethmoid cells. Surgical procedures performed to improve maxillary sinusitis by inferior meatal antrostomy leave residual disease in the ostiomeatal area and may result in persistent mucociliary obstruction. Historically, the possibility of closure following ostial manipulation and the importance of dependent drainage of the maxillary sinus have been cited as arguments against the middle meatal approach. In this study of middle meatal antrostomies the patency rate was 98% between 4 and 32 months. The postoperative endoscopic findings and symptomatic improvement suggest that mucociliary clearance occurs through the surgically widened ostium. We conclude that endoscopic middle meatal antrostomy does not lead to ostial stenosis.