  An analysis of supersymmetric contributions to R_b in supergravity grand
unification with non-universal boundary conditions on soft SUSY breaking in the
scalar sector is given. Effects on R_b of Planck scale corrections on gaugino
masses are also analysed. It is found that there exist regions of the parameter
space where positive corrections to R_b of size $\sim 1 \sigma$ can be gotten.
The region of the parameter space where enhancement of R_b occurs is
identified. Prediction of the full sparticle spectrum for the maximal R_b case
is given. The analysis has implications for the discovery of supersymmetric
particles at colliders.
