  In this talk I begin with some general discussion of model building in
particle theory, emphasizing the need for motivation and testability. Three
illustrative examples are then described. The first is the Left-Right model
which provides an explanation for the chirality of quarks and leptons. The
second is the 331-model which offers a first step to understanding the three
generations of quarks and leptons. Third and last is the SU(15) model which can
accommodate the light leptoquarks possibly seen at HERA.
