Isolated Chinese hamster chromosomes dissociate into a series of specific chromatin subunits approximately the size of stainable chromosome bands upon reduction of the divalent ion concentration during or after isolation. At high pH the chromatin in some bands is differentially removable during chromosome isolation, leaving a banded chromosome with a pattern typical of most G-band procedures. This provides an alternate molecular mechanism to explain the production of banded chromosomes by a variety of staining procedures. These results also suggest an approach to chromatin fractionation, using metaphase chromosomes as a starting material.