Data are presented on the effect of the imbrizin antibiotic on the growth of micromycetes and the ultrastructure of their cellular surface. It is revealed that imbrizin, in 2.5-5.0 mkg/ml concentrations, suppresses considerably the biomass synthesis affects the pellet formation pattern and micellum pigmentation intensity. Under the influence of imbrizin, the cells of micromycetes cultivated in a medium with the presence of an antibiotic, are covered with a thick amorphous layer which is not tightly linked with the cell and is mostly represented by polysaccharides.