The effect of amphotoericin B on the chemical composition of the plasmic membranes of the puppy kidney tissue was studied. It was shown that amphotericin B in a concentration of 10 Units/ml induced changes in the quantitative content of proteins, lipids and RNA in the chemical composition of the plasmic membranes. The effect of amphotericin B on the composition of proteins and lipids in the membranes was also studied. It was found with the method of electrophoresis in polyacrylamide gel that after exposure of the culture cells to the antibiotic significant shifts in the composition of the membrane proteins took place. According to the findings of thin-layer chromatography amphotericin B markedly changed the quantitative content of the fractions in the composition of lipids in the plasmic membranes. Significant deviations under the effect of the antibiotic were observed in the quantitative ratio of separate fatty acids contained in the lipids of the membrane preparations studied. On the basis of the results obtained it was supposed that the mode of action of amphotericin B on the cell was associated with impairement of the plasmic membrane structure by the antibiotic.