The nucleotide sequence of a 1467 bp fragment of Streptomyces hygroscopicus DNA containing the gene (hyg) encoding a hygromycin B phosphotransferase (HPH) has been determined. The N-terminal amino acid sequence of HPH determined by automated Edman degradation has allowed the coding sequence of the hyg gene to be identified. The translation initiation triplet is GTG and 5 bp preceding it there is a sequence complementary to the 3'-end of 16S rRNA from S. lividans. The transcriptional start and termination sites have been determined; the presumptive promoter region has only partial homology to that of the Streptomyces vinaceus vph gene and is different to the promoter sequences of other Streptomyces genes.