We report a bronchial tumor composed of a mixture of oncocytes and carcinoid tumor cells; the latter formed ribbons and pseudoglandular structures in the fashion of a carcinoid tumor. Ultrastructurally, the oncocytic cells showed large numbers of mitochondria but no neurosecretory granules. Although the stem cell of the pulmonary K-cell is unknown, our findings support the notion that both the pulmonary endocrine cells and the oncocytes arise from it.