Treatment of HeLa S(3) cells with actinomycin D during mitosis suppresses the synthesis of several major classes of nonhistone chromosomal proteins during the subsequent period before DNA replication, but allows the synthesis of other species of these proteins. Such results are consistent with the utilization of preexisting, as well as newly transcribed, messenger RNA's for nonhistone chromosomal protein synthesis during the prereplicative phase of the cell cycle.