Grand unification with three generations in free fermionic string models.

We examine the problem of constructing three generation free fermionic string models with grand unified gauge groups. We attempt the construction of G × G models, where G is a grand unified group realized at level 1. This structure allows those Higgs representations to appear which are necessary to break the symmetry down to the standard model gauge group. For G = SO(10), we find only models with an even number of generations. However, for G = SU(5) we find a number of 3 generation models. Address after Sept. 1, 1995: Deptartment of Physics and Astronomy, Rutgers University, Piscataway NJ 08855-0849.