Among 742 patients with cystic fibrosis studied during the past 4 years, 50 (or 6.7%) were found to have nasal polyposis. Polyps were noted in patients of all ages, the youngest being 2½ years of age. Roentgenograms of the sinuses showed evidence of paranasal sinusitis in each case studied. An allergic investigation was conducted in each of the 50 patients with nasal polyposis. Twenty-four patients presented no evidence of allergy. The clinical severity of the basic disease (cystic fibrosis) was the same in both the allergic and nonallergic group. A brief description of the clinical course of the patient with nasal polyps is presented. The polyps are often multiple, may cause complete nasal obstruction, and tend to regrow. Their course is beneficially influenced by the administration of broad-spectrum antibiotics or systemic steroids. However, polyps did appear in many patients while on constant broad spectrum antibiotic therapy. Conservative management is suggested. Simple polypectomy is carried out when nasal obstruction is complete. In a small number of patients, repeated polypectomies have been necessary over a number of years. The severity of the pulmonary lesion is not reflected by the degree of alteration of the mucosal linings of the paranasal sinuses. Patients with nasal polyposis, regardless of the presence or absence of allergy, should be examined for evidence of cystic fibrosis, including family history, pulmonary evaluation, and appropriate laboratory tests.