  We analysis the radial equations for massive Dirac fields in Schwarzschild
black hole spacetimes. Different approximation formulae under the WKB scheme
are developed for the transmission probability ${\cal T}$ of the radial
wavefunction with $E^{2}\gg V_{m}$, $E^{2}\approx V_{m}$, and $E^{2}\ll V_{m}$,
where $E$ is the energy of the field and $V_{m}$ is the maximum value of the
effective potential. Explicit results of ${\cal T}$ in these approximations are
given for various values of $E$, the mass $m$, and the angular momentum
parameter $\kappa$ of the fields. We also discuss the dependence of ${\cal T}$
on these parameters.
