Lipid granulomas were found in histologic sections in 35 (9%) of 400 consecutive aspirated specimens of bone marrow. The granulomas consisted of fat vacuoles of various sizes, macrophages, lymphocytes, plasma cells, eosinophils, and occasional giant cells. Some of the lipid granulomas had an epithelioid, sarcoid-like appearance. The etiology and pathogenesis of lipid granulomas of the bone marrow are not resolved. The appearance of the granulomas is consistent with a reaction to mineral oil. The clinical significance of lipid granulomas lies in their proper recognition so that the differential diagnosis of a more serious granulomatous disease can be avoided.