The v-myb oncogene of the avian myeloblastosis virus has led to the discovery of a large and growing family of myb-related genes in a wide variety of eukaryotes including animals, plants, fungi and slime molds. The Myb-related proteins contain a highly conserved sequence, often present in multiple tandem repeats which constitute a DNA-binding domain. These proteins generally function in the regulation of cell growth and differentiation, often by coregulating gene expression along with DNA-binding proteins of other classes. This review focuses on the evolution of the myb gene family and the role of these genes in development.