PRIMARY tumors of the rib, though uncommon as compared with similar tumors arising in other bony structures of the body, are not so rare as has been supposed. Such new growths are recognized more frequently today than in the past because of the improved diagnostic methods and the more complete knowledge on the part of the clinician, radiologist, surgeon, and pathologist of the nature of these lesions. This greater familiarity with these tumors has led to the erroneous impression that the incidence of rib tumors is rising. That this is not the case becomes obvious from a study of the cases reported in the world literature for the last half-century. Such studies also show that all types of primary neoplasms involving bone and cartilage, in other parts of the skeleton, may also be encountered in the ribs. Though more readily detected in our day than in former years, primary tumors