Lysosome-rich fractions were isolated from rat liver homogenates. In some fractions the lysosomes were separated from the contaminating mitchondria by the use of discontinuous Ficoll/sucrose gradients. Some glycogen was associated with lysosome fractions. This glycogen was of very large molecular size and of a quite different molecular-weight distribution from that isolated from the cytosol. It is suggested that appreciably more than 10% of cellular glycogen is located within the lysosome.
