In the screening programme of organisms producing new antibiotics on selective media with rubomycin (5, 10, 20 gamma/ml) 4 unusual actinomyceteus cultures forming short, straight, hook-like and monospiral spore chains on the aerial mycelium were isolated. The study of the composition of the cell walls showed that they contained meso-diaminopimelic acid and madurose, a differentiating sugar. On the basis of the morphological structure and composition of the cell walls the isolates were classified as belonging to Actinomadura. Comparison of the isolates with the species of Actinomadura described in the literature showed that the isolates were new species of the genera, i.e. Am. roseola sp. nov., Am, aurantiaca sp. nov., Am. vinacea sp. nov. and Am. livida sp. nov.