  Gauge-Yukawa Unification (GYU) is a renormalization group invariant
functional relation among gauge and Yukawa couplings which holds beyond the
unification point in Grand Unified Theories (GUTs). Here, GYU is obtained by
requiring finiteness and reduction of couplings to all orders in perturbation
theory. We examine the consequences of GYU in various supersymmetric GUTs and
in particular the predictions for the top quark mass. These predictions are
such that they distinguish already GYU from ordinary GUTs. Moreover, when more
accurate measurements of the top quark mass are available, it is expected that
it will be possible to discriminate among the various GYUs.
