High-performance and medium-pressure liquid chromatographic techniques were developed for the rapid isolation, identification and characterization of the components from crude virginiamycin and viridogrisein. Two new minor components, denoted virginiamycin Ss and viridogrisein II, were isolated. Their structures were determined by amino acid analysis and mass spectrometry. (I. Oberb&uner er al., Helv. Chim. Acta, 65 (1982) 2280).