We have isolated the Xenopus orthologue of the T-box gene, Tbx20, and characterized its developmental expression profile. We show that Tbx20 is one of the earliest markers of heart tissue in Xenopus, and is expressed throughout all cardiac tissue during later stages of development. In addition, we also observe expression in the cement gland, the jugular vein, the lung bud, the cloacal aperture, rhombomeres 2, 4, 6 and 8, and in a subset of motor neurons.