Spine deformity and chronic pulmonary disease are commonly seen in patients with cystic fibrosis (CF). In order to assess the prevalence of kyphosis, a retrospective evaluation of all initial standing chest radiographs of our CF patients matched with our "reference" population was undertaken. We also studied the possible correlation between the degree of kyphosis and the pulmonary function tests ( PFTs ), consisting of thoracic gas volume and maximal expiratory flows. In our population, the study confirmed an increased prevalence of kyphosis in CF patients (p less than .01), which occurred mostly in girls after 12 years of age (p less than .018). The kyphosis appeared to be, in most instances, of mild degree and was not related to any of the PFTs . No measurable increase of kyphosis was observed over a 3-year period in the group. Longer prospective study and the relationship of kyphosis to endocrine function in CF at puberty should be undertaken.