The DNAase II, Mg-2+ procedure was used to fractionate the seedling chromatin of a heterotic maize hybrid and its parental inbreds FRM017 and FRN28. The hybrid and the more vigorous maize inbred FRN28 have 14 and 11 percent soluble chromatin (euchromatin) respectively, while the less vigorous FRM017 contains 30 percent. The unfractionated chromatin of the hybrid contains less protein than either inbred. The RNA contents of the unfractionated chromatin of the hybrid and of FRN28 are similar and are one-half that of less vigorous FRM017. Hybrid euchromatin contains relatively more protein and RNA than DNA as well as higher proportions of protein and RNA than heterochromatin, unfractionated chromatin, or inbred euchromatin; this suggests a more "efficient" type of activity, as reflected by the low amount of euchromatin and a high proportion of RNA and chromosomal proteins.