Elimination of chromosomes, which is detected by the presence of laggards at telophase, occurs frequently in the spike primordia, but not in the root meristems of the hybrids between H. vulgare cv. Amsel and H. bulbosum L. Cordycepin (10-5M), cycloheximide (10-5M) and colchicine (0.1%) were applied for 30 min to the root meristems of H, vulgare L. cv. Amsel and H. bulbosum L. (4x), and their triploid hybrid E159. Colchicine did not induce laggards at telophase in Amsel, H. bulbosum and hybrid E159, although C-metaphases were observed. Spindle disruption may not be involved in the chromosorne elimination of the hybrids. Cordycepin and cycloheximide induced frequently laggards at telophase in the hybrids at 60 min after the end of the treatments, while no laggards were observed in Amsel and H. bulbosum. Hybrid E159 appears to have the partial suppression of RNA or protein syntheses related to the centromere function, and is sensitive to cordycepin and cycloheximide. Cordycepin and cycloheximide may enhance the suppression of the centromere activity and results in the laggards at telophase. RNA and protein synthesis during G2 or prophase is involved in the chromosome elimlnation in H. vulgre-H. bulbosum hybrids. Cd-staining method, which was reported to distinguish active centromeres from inactive ones of human chromosomes, were modified for chromosomes of Hordeum species. The modified Cd-staining revealed clear centromere dots only in the centromeres. However, both normally separating chromosomes and laggards showed centromere dots. The modified Cd-staining may not stain the centromere structures related to the centromere-microtubule interaction.