The pharmacokinetics of high-molecular-weight polyethylene oxide (HMW PEO)--a parent compound in the polietoks drug--was experimentally studied in cats. A PEO concentration in the blood was determined by measuring a decrease in the hydrodynamic resistance for a blood sample flowing in the turbulent mode via a glass capillary. Variation of the polymer concentration in the blood is described by a single-exponent function with an elimination halftime of T1/2 = 3.15 h. According to the calculation, 99.6% of the initial amount of PEO losses the antiturbulent activity within 24 h.