Fragments spanning 20 kb of Streptomyces nogalater genomic DNA were characterized to elucidate the molecular genetic basis of the biosynthetic pathway of the anthracycline antibiotic nogalamycin. Structural analysis of the products obtained by expression of the fragments in S. galilaeus and S. peucetius mutants producing aclacinomycin and daunomycin metabolites, respectively, revealed hybrid compounds in which either the aglycone or the sugar moiety was modified. Subsequent sequence analysis revealed twenty ORFs involved in nogalamycin biosynthesis, of which eleven could be assigned to the deoxysugar pathway, four to aglycone biosynthesis, while the remaining five express products with unknown function. On the basis of sequence similarity and experimental data, the functions of the products of the newly discovered genes were determined. The results suggest that the entire biosynthetic gene cluster for nogalamycin is now known. Furthermore, the compounds obtained by heterologous expression of the genes show that it is possible to use the genes in combinatorial biosynthesis to create novel chemical structures for drug screening purposes.