Promoter-probe plasmid vectors were used to isolate putative promoter-containing DNA fragments of three Streptomyces antibiotic resistance genes, the rRNA methylase (tsr) gene of S. azureus, the aminoglycoside phosphotransferase (aph) gene of S. fradiae, and the viomycin phosphotransferase (vph) gene of S. vinaceus. DNA sequence analysis was carried out for all three of the fragments and for the protein-coding regions of the tsr and vph genes. No sequences resembling typical E. coli promoters or Bacillus vegetatively-expressed promoters were identified. Furthermore, none of the three DNA fragments found to be transcriptionally active in Streptomyces could initiate transcription when introduced into E. coli. An extremely biased codon usage pattern that reflects the high G + C composition of Streptomyces DNA was observed for the protein-coding regions of the tsr and vph genes, and of the previously sequenced aph gene. This pattern enabled delineation of the protein-coding region and identification of the coding strand of the genes.