A mitochondrial-lysosomal fraction obtained by differential centrifugation of the tail homogenate of metamorphosing Rana catesbeiana tadpoles was fractionated on iso-osmotic self generating gradients composed of modified colloidal silica (Percoll). More than half the activities of most lysosomal hydrolases were recovered to a heavy fraction, which contained little activities of cytochrome oxidase and of catalase. The activities of lysosomal enzymes in the heavy fraction showed latency, and the median density of those was 1.09. These results indicate that intact lysosomes, which are considerably purified, could be obtained by this method.