It was shown with the use of classical and differential polarography that oleandomycin in aqueous solutions undergoes electrolytic reduction on the mercury-dropping electrode. The polarographic wave of the reduction was distorted with adsorption phenomena. Its height was proportional to the analytical concentration of oleandomycin in the solution. The polarographic study on the process of acid and alkaline hydrolysis showed a satisfactory correlation between the height of the oleandomycin peak on the differential polarogramme [Formula: see text] and the biological activity of the antibiotic in the solution. The quantitative analysis implies recording of the data of the differential polarogramme of the test-solution and measurement of the antibiotic concentration with the calibration graph. Comparison of the results of determination of the oleandomycin levels in oleandomycin phosphate drugs and fermentation broth filtrates with the polarographic and micro-biological methods revealed no systematic deviations and showed that the average casual deviation between the results was due only to the errors of the methods reproducibility.