Human colon cancer development is often characterized in an early stage by a hyperproliferation of the epithelium leading to the formation of adenomas. This is mainly a consequence of disregulated cell cycle control and/or suppressed apoptosis as usually observed in colorectal cancers. Dehydrocrotonin is a diterpene lactone obtained from the barks of Croton cajucara Benth (Sacaca) that has several biological activities including hypoglycaemic, antiulcer and antitumor effects. The aim of this study was to analyse the cell cycle and induction of apoptosis by free dehydrocrotonin (DHC) compared with dehydrocrotonin complexed with b-Cyclodextrin (b-CD/DHC) in human colon adenocarcinoma cell lines, Caco-2, displaying features of small intestinal epithelial cells, and HT-29, resembling colonic crypt cells. Human colon HT-29 and Caco-2 cells were incubated with different concentrations of DHC and b-CD/DHC around to IC₅₀ values. Cells (1x10⁶) were suspended in hypotonic solution containing 50 mg/mL of propidium iodide. DNA content was analysed by flow cytometry and the population of cells in each cell cycle phase was determined using Cell ModiFIT software. The experimental work carried out with b-CD/DHC induced cell cycle arrest of the cellular cycle in the sub G0-G1 phase and also apoptosis. These results corroborate the previous data demonstrating caspases activation in treated cells. In conclusion, free DHC and b-CD/DHC work induced apoptosis probably due to cell