To determine the frequency of unusual chest radiographic findings in adults (older than 15 years) with pulmonary tuberculosis, charts and radiographs of 270 consecutive cases seen in a 12 month period were reviewed. Radiographic findings not typical of primary or postprimary disease (reinfection) were arbitrarily classified as unusual. The incidence of such findings (8%) was considerably lower than in several recent reports (25%, 29%). Likewise, the incidence of lower lobe tuberculosis in diabetics in this population (8.3%) was lower than in a report by Weaver (20%), and the finding of air-fluid levels in patients with cavitary disease (9%) was lower than a report by Cohen (22%). Possible explanations for these discrepancies were reviewed, including: (1) demographic characteristics, (2) the patient selection process, (3) the arbitrary nature of any system of classification of "unusual" findings, and (4) the change in the epidemiology of the disease as a result of chemotherapy and organized eradication programs. Of these, the patient selection process is probably the most significant factor in the discrepancy between the incidence of unusual findings in this series compared with those reported by others.