A high resolution gel electrophoresis of histone is described, capable of distinguishing between histone fractions whose mobilities differ by as little as 1%. Under the conditions of pH and urea concentration employed, five major groups of calf thymus histone are distinguished, three of which are further resolved into multiple bands. Thus 95% of total histone is found in ten bands, the remaining five % is in three faint, slow-moving bands. The applicability of this technique for a comparison of histones from a wide variety of species is discussed. © 1969.