- Although calculations of the bs rate in supersymmetric grand unified models have always either ignored the gluino-mediated contribution or found it to be negligible, we show that taking universal supersymmetry-breaking masses at the Planck scale, rather than at the gauge unification scale, as is customary, leads to the gluino contribution being more significant and in fact sometimes even larger than the chargino-mediated contributions when >0 and tan is of order 1. The impact is felt greatest when the gluinos are relatively light. Taking the universal boundary condition at the Planck scale also has an effect on the chargino contribution by increasing the effect of the W-ino and Higgsino-W-ino mediated decays. The neutralino-mediated contribution is found to be enhanced, but nevertheless it remains relatively insignificant. 1995 The American Physical Society.