The Drosophila snail gene is required for proper mesodermal development. Genetic studies suggest that it functions by repressing adjacent ectodermal gene expression including that of the single-minded (sim) gene. The snail gene encodes a protein with a zinc-finger motif, and here we report that the snail gene product is a sequence-specific DNA binding protein. The snail protein recognizes a 14-base-pair consensus sequence that is found nine times in a 2.8-kilobase sim regulatory region. These results provide evidence for the direct control of sim transcription by snail.