The nucleotide sequence (1579 bp) of tetracycline-resistance determinant and flanking regions of the cloned 5.1 kb DNA fragment from Bacillus subtilis GSY908 chromosome (Sakaguchi, R. and Shishido, K. (1988) Biochim. Biophys. Acta 949, 49-57) were determined and compared with those of the B. subtilis tetracycline-resistance plasmid pNS1981. The tetracycline-resistance structural (tet) genes of the B. subtilis GSY908 chromosome (tetBS908) and pNS1981 (tetpNS1981) were found to be highly homologous (80% identical). Both tet genes were composed of 1374 bp and 458 amino-acid residues initiating from a GTG codon preceded by a ribosome-binding site (RBS-2). Upstream from tetBS908 there exists a short open reading frame (20 amino acids) initiating from a ATG codon preceded by its own RBS (RBS-1). This leader sequence was also highly homologous to that of tetpNS1981 except for a deletion of one bp between the RBS-1 and the ATG codon.