• This study evaluated by chart review the clinical, allergic, pathologic, and immunologic characteristics of 20 children found to have chronic bronchitis (CB) by bronchoscopic evaluation, including 13 children In whom CB was documented by endobrochial biopsy. Two additional children likely to have had CB also are described. In this study group, all of the patients were believed to have asthma as well. Chronic bronchitis was predicted by chronicity of symptoms and incomplete response to bronchodilators and corticosteroids, but it was not predicted by a history of allergy or laboratory evidence of systemic infection or inflammation. In the children described herein, CB often was associated with an IgG subclass abnormality. Bronchoscopic evaluation documented CB and provided biopsy and secretion samples. Although the histomorphic findings were heterogeneous, patients with CB usually had white blood cells present on Gram stains of secretions in addition to mononuclear cell Infiltrates on biopsy specimens. Chronic bronchitis in these children seems to be distinct from CB in adults. Further studies will be needed to define CB in children.