An attempt was made to determine the frequency of abnormal maxillary sinus radiographs in a group of unselected children having diagnostic skull radiographs performed for indications unrelated to respiratory infection. An occipitomental, or Water's, view was obtained in every case in order to evaluate the maxillary sinuses. Prior to performance of the radiographs, a history of recent respiratory symptoms was obtained and a physical examination of the ears, nose, and throat was performed. An abnormal maxillary sinus radiograph was defined as one that revealed an air-fluid level, partial or complete opacification, or mucous membrane thickening of 4 mm or greater. Fifty-nine (53%) of 112 presumably "normal" children had evidence of recent respiratory inflammation by history or at physical examination. In 50 subjects less than 1 year of age, abnormal maxillary sinus radiographs were common, irrespective of respiratory symptoms and signs. In contrast, eight of 14 children (57%) aged 1 to 16 years with both symptoms and signs of respiratory inflammation had abnormal maxillary radiographs, compared with only two of 31 children (7%) with neither symptoms nor signs (P less than .005). Crying alone was not associated with abnormal radiographs in the older age group. In children more than 1 year of age, abnormal maxillary sinus radiographs are infrequent and are generally related to inflammation of the upper respiratory tract.