  We discuss the effects of QCD corrections to the on-shell decay $t \to b W$.
We resolve the scale ambiguity using the Brodsky-Lepage-Mackenzie scheme, and
find that the appropriate coupling constant is $\alpha_{s}^{ \overline{MS}}
(0.122m_{t})$. The largest long distance contribution comes from the definition
of the on-shell mass of the top quark. We note that QCD corrections to the
electroweak $\rho$ parameter are extremely small when the $\rho$ parameter is
expressed in terms of the top quark width.
