Kinetics of the reactions of ampicillin and oxacillin peroxyacidic oxidation and perhуdroliysis with potassium peroxomonosulphate in the alkaline medium by product light adsorption was studied. The procedure and the possibility of quantitative determination of ampicillin and oxacillin in the Ampiox preparation by the kineticspectrophotometric and iodometric methods were developed. RSD ≤ 1.5 % ( δ = 1,.4..– 0.5 %).