The nucleotide sequence of the alcohol dehydrogenase gene Adh71k has been determined. The Adh71k allele encodes the thermostable and multifunctional ADH-71k allozyme of Drosophila melanogaster. Comparison with the sequences of AdhS, AdhF, and AdhFChD reveals differences in the coding and noncoding regions of the gene. Conceptual translation of the Adh71k sequence indicates that ADH-71k shares with ADH-F and ADH-FCHD an amino acid replacement at residue 192 and with ADH-FCHD an additional replacement of serine for proline at residue 214. Three unique differences were found in the nontranslated regions. It is proposed that a nucleotide deletion in the adult intron is related to the difference in expression level of the Adh71k allele, relative to the other alleles. An insertion of five nucleotides, additional to a single base deletion at that site, was detected in one of the larval enhancer regions in the 5' flanking region of the Adh71k allele, creating a palindromic structure in that area.