A case of a 34-year-old woman with three histologically proven coincidental granular cell tumors is reported and documented with electron microscopic observations. The subject of multicentric occurrence of these rumors is reviewed in the literature and the available data and circumstances with a possible bearing on their nature are discussed. From the number of reviewed case reports (550) it appears that the occurrence of multiple granular cell tumors (36) is much more common (7 to 16%) than traditionally believed. Attention is drawn to their benign course. The precise histogenesis of these tumors and the chemical nature of the 160 to 240 Å vesicular units of the granules remain unknown. The authors conclude that the granular cells in this instance are of mesenchymal derivation and that the granules of these cells may represent the end result of an obscure metabolic alteration manifested by intracytoplasmic storage of protein and lipoid substances.