In recent decades, first-principles methods of computational electronic-structure theory have provided extremely powerful tools for predicting the electronic and structural properties of materials, using only the atomic numbers of the atoms and some initial guesses at their coordinates as input. My principal interests are in applying such methods to study the dielectric, ferroelectric, piezoelectric, and magnetoelectric properties of oxides. These may be simple bulk materials, or they may be superlattices or other nanostructured composites in which surface and interface effects are important. I also have an abiding interest in the development of new theoretical approaches and computational algorithms that can extend the reach and power of these first-principles methods. In particular, our group has made contributions to pseudopotential theory, the theory of electric polarization, the study of insulators in finite electric fields, the theory of Wannier functions and their applications, and the role of Berry phases and Berry curvatures in dielectric and magnetoelectric phenomena.