Myoskeletin was identified as a gene induced by activin in animal cap explants of Xenopus laevis. This gene encodes a protein related to the transcription factor Myocardin. Whereas Myocardin is expressed in the heart and is known to be involved in heart and smooth muscle formation, Myoskeletin is expressed in the somites and in hypaxial muscle precursors as they migrate away from the somites during tadpole stages. Myoskeletin is required for hypaxial muscle formation, as reduction of its expression through injection of an antisense morpholino oligonucleotide leads to suppression of hypaxial muscle formation. In overexpression experiments in animal caps, Myoskeletin is capable of inducing multiple genes including skeletal muscle, cardiac muscle and smooth muscle-specific genes. We conclude that Myoskeletin is a somite and hypaxial muscle-specific member of the Myocardin family that is required for hypaxial muscle formation.