  We calculate the radiative corrections to the nonleptonic inclusive B decay
mode $b\rightarrow c\bar u d$ taking into account the charm quark mass.
Compared to the massless case, corrections resulting from a nonvanishing c
quark mass increase the nonleptonic rate by (4--8)\%, depending on the
renormalization point. As a by--product of our calculation, we obtain an
analytic expression for the radiative correction to the semileptonic decay
$b\rightarrow u\tau\bar\nu$ taking into account the $\tau$ lepton mass, and
estimate the c quark mass effects on the nonleptonic decay mode $b\rightarrow
c\bar c s$.
