  The contribution of gravitational wave (tensor metric) and energy density
(scalar metric) fluctuations to the cosmic microwave background polarization is
computed by numerically solving the relativistic radiation transfer equations.
We find that the tensor contribution is significant only at large angular
scales (multipoles $\ell \lta 40$). For standard recombination, the tensor
contribution can dominate at $\ell \lta 40$; however, the effect would be
difficult to detect since the total (scalar plus tensor) polarization is $<
1$\%. For models with late reionization, the total large angular scale
polarization is large ($\sim 7-9$\%), but the tensor fraction is negligibly
small. Hence, polarization may be useful for discriminating ionization history,
but is much less promising as a means for detecting tensor fluctuations.
