The three polyene macrolide antibiotics, fungichromin, lagosin, and cogomycin, previously described as having some stereochemical differences at one or more centers, are shown by countercurrent distribution, high-performance liquid chromatography, carbon-13 nuclear magnetic resonance spectroscopy, circular dichroism, and biological studies to be identical in all respects, including stereochemical aspects. The differences observed earlier in their properties have now been ascribed to varying amounts of impurities, which are separable by high-performance liquid chromatography. All three antibiotics contain one major and several minor components.