We have investigated binding of the lectins wheat germ agglutin (WGA) and concanavalin A (Con-A) to mitotic chromosomes and interphase nuclear substructures using fluorescein and rhodamineconjugated lectins. Standard cytogenetic preparations of human lymphocyte chromosomes were incubated with WGA. Mitotic chromosomes and interphase nuclei are brightly fluorescent. Con-A did not detectably bind chromosomes prepared in this way. Mitotic chromosomes display a distinctive banding pattern with WGA similar to quinacrine banding. We also studied binding to interphase "nuclear scaffolds", which are prepared by treating isolated Hela cell nuclei with DNAse l and high salt. WGA binds nuclear scaffolds internally while Con-A binds to the periphery. The specific binding of lectins to chromosomal structures derived from these two different methods indicates that glycosides are true chromosomal components and that glycoproteins may have a role in chromosome organization.