This chapter begins with the discussion on molecular control of development of tooth. Following important questions are answered in this section: How is the oral-aboral axis formed? How are the sites of formation of tooth decided? How do the genes control the formation and function of the enamel knot? How are the tooth type and their correct position determined? The genetics of tooth agenesis is dealt in detail. The role of Pax-9 and Msx-1 genes in the embryological development of teeth and their mutation is described at length. Similarly, genes involved in amelogenesis imperfecta (ENAM, AMLEX, MMP20, KLK4 and DLX3) are mentioned with their mechanism of action. The genetics of all types of dentinogenesis imperfecta (shields type I, II and III) is described with reference to gene DSPP. This chapter concludes with the genetics of dentine dysplasia and hypophosphatasia.