The oligomer chromatin fragments relatively uniform in size (8--11 nucleosomes) were prepared by a short-term endonycleolysis. The heterogeneity of these fragments with respect to their electrophoretic mobility was revealed using free flow electrophoresis. The individual fragmentated chromatin subfractions were obtained. These subfractions differed in their protein and RNA content per DNA weight unit, in quantitative ratios of different zones of high molecular weight non-histone proteins and in thermal and alkaline denaturation kinetics. It was also found that the parameters investigated are correlated with electronegativeity of the fragmentated chromatin subfractions.