Among the benign thoracic neoplasms, pulmonary hamartomas have been considered one of the most innocent. The 10 patients whose cases are reported in this paper had lesions of this type which we have considered worthy of recording because all of the tumors showed varying degrees of enlargement on roentgen examination. The tumors were considered possible carcinoma in nine instances and tuberculoma in one before a definite pathologic diagnosis was made. REPORT OF CASES Case 1. —S. M. (VAH 151921), a 38-year-old white man, was admitted to the hospital, Sept. 6, 1950, because of a round lesion of the left lung which had increased 1.0 cm. in diameter during the preceding year. The patient had no pulmonary symptoms, and physical examination revealed no abnormalities. Skin tests to PPD, blastomycin, coccidioidin, and histoplasmin were negative. Bronchoscopy was not contributory. Roentgenograms of the thorax (Fig. 1) revealed a round lesion, 1.5 cm. in