Letters to the Editor 841 "raise significant doubts as to the validity of our conclusions," but rather illustrate how much more we need to know regarding nasal cavity and paranasal sinus disease in patients with CF. We would like to make several counterpoints.Firsl, this manuscript attempted to provide insight into functioaal endoscopic sinus surgery (FESS) in patients with CF in a prospective manner. It is the first prospective study. Although some information regarding patients who did not undergo FESS was provided, a major intent of these data was to serve as a historical database for other prospective studies on surgical and medical management, or in the study of the natural history of this disease, which remains poorly understood. We already understand the criticism regarding the mean follow-up of only 34 months. We also understand that FESS does not directly address the pathophysiology of the disease. Consectuently, these patients will be followed up long term, as are off~er patients with CF who are treated nonsurgically. Patients in this CF study group were offered FESS as an additioaal therapy to improve symptoms and clinical signs perceived by patients and/or parents beyond their medical therapy. No prospective information on the efficacy of FESS currently exists. The potential consequences of pediatric sinus surge D' in general are also appreciated, particularly after the report ~y Mair et al. t on changes in sinus morphology after FESS s;urgery in pigs.No comment can be made regarding the purported results in the paper presented by Marks et al. presented at the ARS in New O,fleans last fall because it has not been published. We will be very interested in reviewing the paper, particularly the study's design and method of analysis. We hope their letter was not a vehicle to bring attention to their study.The comment regarding "minimal or no impact on the postoperative endoscopic examination or CT scan" is not entirely accurate. Although postoperative CT scans still exhibit significant mucosal thickening after surgery, a common eharacleristic of medial bulging of the lateral nasal wall seen before .,~urgery did not recur during the study interval. In regard to postoperative endoscopic findings, while abnormalities still persisted they were often ameliorated, which seemed to correlate with symptom improvement. Because the pathophysiology of this disease is not directly affected, the assumption that patients will relapse is logical. However, we do not know this to be true based on "data." It is an issue that needs to be clarified. More importantly, this points to the fact that we need to develop a better understanding of the natural history of the disease. Reviewing serial CT scans from childhood to young adulthood, we have casually observed that in some patients radiographic paranasal sinus disease may naturally improve over time. Furthermore, we believe that the clinical expression of this disease varies widely, and an understanding of why this occurs given the identifiable gene defect deserves closer exam...