The mobilization of food reserves and ultrastructural changes in th cotyledons of germinating soybean seeds (Glycine max L. Mer. Cultivar Amsoy) and seedlings were studied by using light and transmission electron microscopy. When germinating began, the cotyledon tissues were packed with protein an lipid bodies. Mobilization of the reserves started in epidermis and vascular bundles. After three days of seedling growth, significant reductions of protein and lipid bodies were observed; concurrently, the numbers of starch grains, glyoxysoms, and mitochondria were increased. These ultrastructural changes are discussed with reference to the metabolism of the germinating soybean seeds and seedlings.