An important goal of modern dentistry is to preserve a functional, esthetic, and pain-free dentition. If irreversible pulp pathology occurs in an immature permanent tooth from traumatic or carious exposure, normal apical maturation may be interrupted. Conventional endodontic obturation techniques, if necessary, will be difficult and may not be adequate in such a tooth. The endodontic techniques of apexogenesis and apexification have been successful in achieving adequate root development and apical construction. These conventional techniques and materials are reviewed along with a promising material called mineral trioxide aggregate.