The importance of a solitary circumscribed mass in the lung has attracted increasing recognition in recent years. As a result of the extended use of roentgenologic examination of the chest, detection of these lesions is now commonplace. Advances in thoracic surgery have resulted in an effective means of definitively managing these lesions. As a consequence, complacency is no longer justifiable on the part of an attending physician who discovers such a lesion with its recognized malignant potentiality. Circumscribed mass lesions of the lung are generally peripheral in location with respect to the pulmonary hilus. Because of this, important clinical problems in management and diagnosis arise. In the first place, symptoms develop less commonly and at a later stage than those caused by lesions lying close to a central bronchus. Consequently, it is more difficult to impress on the patient the importance of assuming an active approach toward the management of