Whole histone extracted from chromatin by either acid or protamine displacement was found by gel electrophoresis at pH 7 to contain only two histone complexes, H2A–H2B and H3–H4, and uncomplexed histone H1. Although both complexes are dissociated at low pH or with high urea concentrations, removal of the denaturant resulted in complete complex reformation within minutes at the most. A systematic investigation of binary, ternary and quaternary histone mixtures revealed that interactions also occur between histones H2B–H4 and H2A–H4. No evidence however was found for the formation of ternary and quaternary histone complexes.