Abstract: The biotransformation of etheofazine (EDMTP), a new anticancerdrug, was studied by using isolated perfused rat liver. Two main metabolites were sepa-rated from the perfusate by HPLC and TLC and their chemical structures were determinedby MS,¹H-NMR and IR. EDMTP-I is the parent compound. EDMTP-II is7-ethyl-8-aminotheophylline. EDMTP-II was also separated and identified from theblood of mice atter iv of 10 mg/kg. Species difference of biotransformation of EDMTP be-tween rat and mouse seems to be not significant in this study.