Abstract: This paper depicted results of the investigation on the physiological disposition of ³H-indirubin and its derivatives ³H-79002 and ³H-79005 in mice and rats.All the examined compounds were found to be poorly absorbed from the gastrointestinal tract of mice, but ³H-79002 was absorbed more rapidly and moreCompletely than ³H-indirubin, ³H-79005 was absorbed less rapidly and less completely.In tumor tissue of Lewis lung cancer, the radioactivity of ³H-79002 was about twice as high as that of the other two compounds. Only in the gastrointestinal tract was the radioactivity of ³H-79005 much higher than that of the other two com pounds at 12-hr after oral administration.Examination of the metabolites of these compounds by TLC revealed that there was very little radioactivity of unchanged compound in every group, most of the radioactivity appeared as various metabolites. According to the analysis of the urine in animals treated with ³H-79002 or ³H-79005 by using TLC, about 1/3 of the total radioactivity on the chromatogram behaved as ³H-indirubin.These results showed that the differences in physiological disposition of these three compounds might be one of the factors influencing their antitumor activity.