OBJECTIVE: To investigate absorption mechanisms of Zedoary Turmeric oil (ZTO) by Caco-2 monolayers model. METHODS: Caco-2 cell model was applied to investigate the transportation of ZTO and its active components, including curdione, germacrone, furanodiene and curcumol. Permeability coefficients of above active compounds and ZTO across Caco-2 cell monolayers were measured as a function of direction transport and concentration of each component. In addition, the effects of other components on the permeability of curdione and germacrone were also investigated. RESULTS: The apparent permeability coefficients (Papp) of curdione, germacrone and curcumol were high. Compared with transcellular marker propranolol, the apparent permeability coefficients of curdione, germacrone and curcumol were not significantly changed by transport direction and drug concentrations (P > 0.05). Furanodiene and other high lipophilic components in ZTO (e. g. furanodiene, curzerene and β-elemene) did not transport across Caco-2 cell monolayer. Components other than selected compounds in ZTO did not interfere the permeability coefficient of curdione and germacrone (P > 0.05). No metabolites were detected in receiver side during the transport study with ZTO and selected active compounds. CONCLUSION: The above results indicate that transcellular transport was dominated by passive diffusion for ZTO and its selected active components. The high lipophilic components in ZTO, e. g. furanodiene, could not transport across the Caco-2 monolayer and most of them were uptake into cell monolayers and could not reach to receiver side. Other components in ZTO did not influence the transport of the active essential oil.