Total histones increased the permeability of lysosomal membranes for enzymes of matrix in the preparation of isolated lysosomes, where free and nonsedimented activity of acid phosphatase was estimated. The phenomenon depended on concentration of histones in a mixture. Histones apparently destructed the lysosomal membranes at concentration of 100 mg/ml and higher, since the level of free and nonsedimented activity of acid phosphatase approximated and even exceeded the enzymatic activity after treatment of the lysosomes with 0.2% Triton X-100. These properties of histones depended on their macromolecular structure. Histones did not affect the activity of the solubilized enzyme.