We show for the first time that aneuploid cells overexpress CDC20 (but not the APC/C subunits), both across human cancer cell lines and in two experimental models of aneuploidy induction (by tetraploidization or by Reversine treatment), potentially explaining the increased inherent chromosomal instability in these cells and their enhanced sensitivity to the excess CIN caused by SAC inhibition. The gene discussed is CDC20; the disease is cancer.