  We study radiative corrections to third generation scalar fermions into gauge
bosons $Z$ and $W^\pm$. We include both SUSY-QCD, QED and full electroweak
corrections. It is found that the electroweak corrections can be of the same
order as the SUSY-QCD corrections and interfere destructively in some region of
parameter space. The full one loop correction can reach 10% in some SUGRA
scenario, while in general MSSM, the one loop correction can reach 20% for
large $\tan\beta$ and large trilinear soft breaking terms $A_b$.
