[en] Effect of 2-hydroxypropyl α-cyclodextrin (α-HPCD) on the iodine adsorption onto activated carbon (AC) was investigated. The iodine sorption efficiency increased with the sorption time, but the rate of increase in the sorption efficiency varied depending on the α-HPCD concentration. As a result, there were significant differences of up to 3 times in sorption efficiency between the α-HPCD concentrations in the sorption time of 3 days. There was almost no difference in the sorption efficiency between the α-HPCD concentrations in the sorption time of 10 days. It is considered that the sorption speed increased, because the molecules number increases and the affinity of iodine for AC increased as the iodine is included into α-HPCD. (author)