The nucleotide sequence of the class G tetracycline resistance determinant previously isolated from Vibrio anguillarum has been determined. Two open reading frames of divergent polarity were identified. A resistance gene (tet A) encodes a protein of 393 amino acid residues (deduced molecular mass of 40.9 kDa), and a repressor gene (tet R) encodes a protein consisting of 210 amino acids with a calculated molecular mass of 23.6 kDa. Based on the deduced amino acid sequences, the proteins of tet A(G) and tet R(G) are about 60% homologous with those of RP1/Tn1721 (class A) and pSC101/pBR322 (class C), and about 50% homologous with Tn10 (class B). The relationship of the tet (G) sequence to five known tetracycline resistance determinants (class A to E) is discussed.