Abstract: Doxophylline, a new antibronchospastic drug, being more active and less toxic than aminophyline, was detected by high performance thin layer chromatography. The pharmacokinetics of doxophylline have been characterized in rats, whose serum concentration were monitored after 100, 200, 400 mg·kg^-1 oral dose. The drug was found to conform to a one compartment model and can be bio transformed quickly in rats. The Cmax, AUC and CL/F appeared to be dose dependent. T_1/2(Ke) was 1.17±0.13 h after the 100 mg·kg^-1 dose, 2.54±0.60 h after the 200 mg·kg^-1 dose and 3.75±0.92 h after the 400 mg·kg^-1 dose. The doxophylline concentration in tissues decreased rapidly. Total excretion of the drug in urine, bile and faeces was 5.2 per cent of the dose. Plasma protein binding was about 25 percent.