Tubulin has been implicated as a nuclear protein because of the role it plays in mitosis. In this paper we examined the role of tubulin in the nuclei of nonmitotic cells. Tubulin was found distributed throughout the nucleus and particularly in association with the chromatin. It comprised about 6.5% of the nonhistone chromosomal proteins. Nuclear tubulin appeared to be nonmicrotubular in form. Fluorescence microscopy data on metaphase chromosomes revealed that tubulin was present on the outside of the chromosomes. These data suggest a structural role for chromatin-associated tubulin.