ergosterol exhibits the strongest interaction with amphotericin B and B-sitosterol the weakest. Cholesterol and stigmasterol show interme-diate behaviour. As a consequence of the interactions, deviations from ideality are ob-served; negative at low and positive at high surface pressures. 1'he interactions are most pronounced for monolayers with the mole fraction of amphotericin Xa == 0.5 and 0.7 which lea.ds to the formation of an amphotericin B-sterol complexes of 2:1 stoichiometry. The obtained results support pharmacological assumption that amphotericin B has a greater affinity to ergosterol than to other sterols. Also the presence of amphotericin B-sterol com-plexes of 2: 1 stoichiometry, responsible for the formation of channels in cell membranes, has been confirmed.