The GATA transcription factors are a family of C4 zinc finger-motif DNA-binding proteins that play defined roles in hematopoiesis as well as presumptive roles in other tissues where they are expressed (e.g., testis, neuronal and placental trophoblast cells) during vertebrate development. To investigate the possibility that GATA proteins may also be involved in Drosophila development, we have isolated and characterized a gene (dGATAa) encoding a factor that is quite similar to mammalian GATA factors. The dGATAa protein sequence contains the two zinc finger DNA-binding domain of the GATA class but bears no additional sequence similarity to any of the vertebrate GATA factors. Analysis of dGATAa gene transcription during Drosophila development revealed that its mRNA is expressed at high levels during early embryogenesis, with transcripts first appearing in the dorsal portion of the embryo just after cellularization. As development progresses, dGATAa mRNA is present at high levels in the dorsal epidermis, suggesting that dGATAa may be involved in determining dorsal cell fate. The pattern of expression in a variety of dorsoventral polarity mutants indicates that dGATAa lies downstream of the zygotic patterning genes decapentaplegic and zerknullt.