In this study, we noted that fucoidan at a concentration of 5 - 20 μg/mL 1) increased the activation of caspases, 2) reduced the protein levels of IAPs, 3) increased mitochondrial membrane permeability and cytochrome c and Smac/Diablo release, 4) increased the levels of Bak and t-Bid but reduced the levels of Mcl-1, and 5) increased the levels of Fas, DR5, and TRAIL in HT-29 human colon cancer cells. The gene discussed is CYCS; the disease is malignant colon neoplasm.