There are two basic theoretical approaches to obtaining neutrino mass and mixing. In the minimalist approach, one adds just enough new stuff to the Minimal Standard Model to getm&ngr;≠0andU&agr;i≠1.In the holistic approach, one uses a general framework or principle to enlarge the Minimal Standard Model such that, among other things,m&ngr;≠0andU&agr;i≠1.In both cases, there are important side effects besides neutrino oscillations. I discuss a number of examples, including the possibility of leptogenesis fromRparity nonconservation in supersymmetry. ©2000 American Institute of Physics.