A cDNA encoding a putative alcohol dehydrogenase (ADH) class III was cloned from the silkworm, Bombyx mono The full length cDNA is 1,385 nucleotides long and contains an open reading frame of 1,128 bp encoding 376 amino acid residues. The B. mon ADH III protein sequence was aligned with ADH III known from various organisms. Interestingly, the protein sequence of B. mon ADH III showed 87% and 85% identity to ADH III from marine fish Sparus aurata and Branchiostoma floridae, respectively, whereas rather low sequence identity (83%) to Drosophila melanogaster ADH III was observed. Northern blot analysis revealed that B. mon ADH III mRNA is expressed in all tissues from larva examined: fat body, midgut, epidermis, silk gland and ovary, with the highest level found in the fat body.