The GATA family of nuclear factors has been implicated in the regulation of cell type-specific transcription. We report the isolation of theXenopusGATA-4 and GATA-6 cDNA clones and characterize the expression patterns of the xGATA-4/5/6 genes. By comparing the sequence of the cDNAs with those previously reported from chick and mammalian sources, we conclude that each is conserved across vertebrate evolution as a distinct gene product. Each gene is expressed in differentiated adult heart and gut, but maintains distinct transcript patterns in various other adult tissues. During embryogenesis, each gene displays a similar overlapping distribution of transcripts localized throughout the developing cardiogenic region. The xGATA-4 gene can be detected in dorsal cardiac progenitor rudiments prior to migration. Axis disruption experiments were used to demonstrate that transcription of these genes is intimately associated with the specification of cardiac progenitors. Ectopic expression of each gene is specifically capable of activating during embryogenesis the transcription of the cardiac genes encoding actin and myosin heavy chain α. The data are consistent with a primary role for the GATA-4/5/6 genes in regulating heart development.