THE INCREASED interest in thoracic diseases in the past decade has brought to light a relatively new class of patients, those with solitary pulmonary lesions. Probably the greatest factor in bringing many of the asymptomatic patients to treatment has been the use of general survey x-ray films by industry and city health programs. The routine use of admission films of patients entering hospitals for extrapulmonary complaints has added to this group. The general practitioner also has taken an increased interest because of the demand for routine physical examinations in supposedly healthy persons. Finally, many patients with pulmonary lesions demand an exact diagnosis because of the stress of lay publications, another influence which brings persons to their physicians for earlier diagnoses. In the past it has been the practice of many physicians when confronted with such a single pulmonary lesion to follow a program of "watchful waiting." It soon became apparent