We have reintroduced an 8 kb genomic fragment from theDrosophilatyrosine hydroxylase (DTH) locus into the genome of mutantpale (ple)flies.plewas first recovered as a recessive embryonic lethal by Jurgenset al.(1984) and maps to the same chromosomal region as DTH (65A-E). Mutantplealleles affect pigmentation of the cuticle (L-DOPA, the product of the reaction catalyzed by TH, is an intermediate in the cuticular sclerotization and pigmentation pathways) and catecholamine biosynthesis. In this report we demonstrate that ple does encode the structural gene for TH, since the reintroduced sequences rescuepleflies from lethality to viable adults. Morphological, immunocytochemical, and behavioral characterization of three transformant lines suggests that the reintroduced sequences contain the necessary elements for correct temporal and spatial expression of the gene, but may not contain all the sequences essential for quantitative expression.