Because many malignant and benign processes may manifest as a solitary pulmonary nodule on a chest roentgenogram, this finding presents a diagnostic challenge. The major concern is whether the lesion is malignant. The likelihood of a malignant tumor correlates with the age of the patient, the size of the nodule, a history of a prior malignant lesion, and a history of smoking. Recent advances in radiologic techniques, such as the detection of calcium or the inference of the presence of calcium by high attenuation values on computed tomography, provide assistance in identifying benign lesions. The history, physical examination, and radiographic information can help determine an appropriate course of action. The goals are to remove malignant nodules promptly and to avoid surgical intervention in patients whose nodules are benign.