A reversed-phase high-performance liquid chromatography method has been developed for the determination of proxodolol in the blood serum and tested in rabbits. The HPLC measurements were carried out using a Phenomenex (LUNA) C18 (5 μm) column eluted with acetonitrile-1 mM sodium pentylsulfonate (25: 75, v/v) mixture adjusted at pH 3.0 with phosphoric acid; eluent flow rate, 1 ml/min. The UV detector was tuned to 272 nm. Sample preparation: to 0.5 ml of blood serum in a 10-ml glass centrifuge tube is added 100 μl of 2.5 N NaOH and 4 ml chloroform; the mixture is shaken for 2 min and centrifuged at 3000 rpm for 10 minutes. The chloroform phase is separated and evaporated to dryness in a flow of nitrogen. The residue is dissolved in 100 μl of 1-mM sodium pentylsulfonate (pH 3); a 50 μl aliquot is introduced into the HPLC column. The proposed method is simple, rapid, sensitive, and has a good linearity. The average recovery of proxodolol is 80%. The drug detection limit is 0.015 μg/0.5 ml. The method is linear in the interval from 0.02 to 1.0 μg/0.5 ml with a correlation coefficient of 0.9996. The coefficient of variation is below 2% within a day (n = 5). The method was used for determining the parameters of proxodolol pharmacokinetics upon peroral administration in a dose of 40 mg in rabbits.