The use of 5-fluorouracil (5-FU) in colon cancer as the primary chemotherapy has not been meet satisfactory effectiveness. Therefore, the development of new chemicals as a chemopreventive agent and a combination agent (co-chemotherapeutic agent) for colon cancer is important. Pentagamavunone-0 (2,5-bis-(4'-hydroxy-3'-methoxybenzylidine) cyclopentanone) (PGV-0), one of curcumin analogs, exhibits cytotoxic effect and apoptosis induction in various cancer cell lines, including colon cancer cell, better than curcumin. This study aimed to investigate the cytotoxic potency of PGV-0 in combination with 5-FU and their effects, in single or in combination, on cell cycle toward WiDr colon cancer cell line. The cells were treated with combination concentrations of PGV-0 and 5-FU, and examined by MTT cell viability assay. The value of combination index (CI) as a parameter of cytotoxic combination assay was measured by a combination index method. Cells were stained with propidium iodide and the cell cycle distribution was determined by flowcytometry. CI calculation showed additive effects between PGV-0 and 5-FU. Combination of PGV-0 and 5-FU gave synergism on cell cycle. Single treatment of PGV-0 increased apoptosis, illustrated as subG1-phase accumulation, stronger than single treatment of 5-FU. Meanwhile, combination of PGV-0 and 5-FU demonstrated S-phase arrest. Based on these results, it can be concluded that PGV-0 has the potential to be developed as a co-chemotherapeutic agent for colon cancer but still requires further tracking of its molecular mechanisms. Keywords: Pentagamavunone-0 (PGV-0), 5-fluorouracil (5-FU), colon cancer,combination, cell cycle