Two antibiotics have been isolated from a strain of Rhodococcus fascians that emerged from a competitive co-culture with Streptomyces padanus. The structures of these compounds were elucidated by detailed analyses by NMR and MS. They belong to the aminoglycoside family of antibiotics, and they are structurally unrelated to the actinomycins that are produced by S. padanus. The compounds have been named rhodostreptomycins A and B, reflecting their rhodococcal origin and streptomycin-like composition. Rhodostreptomycins exhibit antibiotic activity against a range of Gram-positive and Gram-negative bacteria.