A method is presented for mass isolation of metaphase chromosomes and nuclei from plant protoplasts. The isolation procedure was developed for both monocotyledonous and dicotyledonous species using wheat (Triticum monococcum) and poppy (Papaver somniferum) cell cultures. Metaphase chromosomes were isolated from partially synchronized mitotic protoplasts, while for the isolation of nuclei unsynchronized protoplasts were used. Light and electron-microscopic studies revealed that isolated chromosomes and nuclei preserved their intact morphology. A preliminary biochemical study of chromosomal proteins was made by polyacrylamide-gel electrophoresis. Because of the purity and high quantity of isolated chromosomes and nuclei, the given isolation procedure can supply useful material for structural and biochemical studies, and for genetic manipulation.