  We reconsider how Yukawa couplings may be determined in terms of a gauge
coupling through the infra-red fixed point structure paying particular regard
to the rate of approach to the fixed point. Using this we determine whether the
fixed point structure of an underlying unified theory may play a significant
role in fixing the couplings at the gauge unification scale. We argue that,
particularly in the case of compactified theories, this is likely to be the
case and illustrate this by a consideration of phenomenologically interesting
theories. We discuss in particular what the infra-red fixed point structure
implies for the top quark mass.
