The Cu-Zn superoxide dismutase (SOD) cDNA and genomic DNA from Drosophila melanogaster have been isolated. The sequence of the coding region for the Sod gene as well as 413 bp of the 5'-untranslated region, 247 bp of the 3'-flanking DNA, and the single 725-bp intron have been determined [Seto et al., Nucleic Acids Res. 15 (1987) 10601]. The sequence reveals an additional C-terminal triplet coding for valine not found in the mature SOD protein. The nucleotide sequence of the coding region has 56% and 57% homology compared with the corresponding human and rat Sod genes, respectively. The codon usage for the Sod gene is similar to that found for other Drosophila genes. The gene hybridizes to position 68A4-9 on Drosophila polytene chromosomes. In addition, in wild-type Drosophila the Sod cDNA hybridizes to a 0.7-0.8-kb transcript which is greatly diminished in a Sod 'null' mutant that produces only 3.5% of the SOD protein.