An endobronchial lipoma has been studied with light, scanning, and transmission electron microscopes, and the literature has been reviewed. Endobronchial lipoma is a type of hamartoma unique only in terms of its specific adult-type fat cell and its location. Of 49 endobronchial lipomas, eight have been reported in obese persons. The neoplasm appears to propagate at its peripheral zone through continuous incorporation and fusion of globules of fat in the spindle-shaped precursor cells. Although benign pulmonary tumors make up about 3 percent and endobronchial lipomas only about 0.1 percent of all pulmonary tumors, benign endobronchial tumors may cause unnecessary morbidity and mortality if not properly managed.