Streplomyces tenebrarius H6 produces a complex of aminuglycoside antibioties. such as apramycin, tohramycin and kanamycin B etc. To study the apramycin hiosyrthetic genes the genomic library from the Streptonyces tencbrarius H6 was estahlished using E. coLi Strepiomyces shuttle vector pKC505 by in vitro packing. The prolbability of finding a specific gene from the litirary composed of 3000 colcnies was over 99.9%. Accurding ro thc highly conserved sequence of the genes involved in 6-de-oxyhexose biosynLhesis, primers were dcsiened and 0.6kb fragment homologous to strE gene was obtained by PCR.30 positive cLones were found from the genmnic librarv of S. tennbrarius H6 with the 0.6kb fragment as a probe. Overlapped regions were localized by Southern hybridization and pulative sugar relaled biosynthciic gene cluster uas mapped hy restriction enzyjne digcstions. An ORF or dTDP-ducosc-4, 6-dehydratase gene consisted of I, 132bp. designatcd as aprE, was obtained and submitted to GenBank under the accession number of AF306787. A DNA sequence hiehly homologous to strLcoding dTDP-4-dehydrorhamnose reductase was found linked with aprE gene.