Lovastatin (monocolin K) is a competitive inhibitor of 3-hydroxy-3-methylglutaryl-CoA-reductase. Its influence on the growth of a lovastatin sensitive strain of Rhodotorula rubra, the biosynthesis of ergosterol and the resistance to polyenic antibiotics was studied. It was shown that the lovastatin action on the strain depended on the inhibitor dose. In a concentration of 0.1 to 0.5 micrograms/ml lovastatin inhibited the yeast growth and ergosterol biosynthesis. Higher concentrations of the inhibitor in the medium led to the recovery of the sterol biosynthesis. It was also demonstrated that a decrease of the ergosterol level in the cells under the influence of lovastatin resulted in the development of resistance in the yeast to polyenic antibiotics such as nistatin and amphotericin B. Correlation between the ergosterol level in the yeast cells and their susceptibility to the polyenic antibiotics was observed.