  We have studied finite temperature corrections to the baryon transport cross
sections and diffusion coefficients. These corrections are based upon the
recently computed renormalized electron mass and the modified state density due
to the background thermal bath in the early universe. It is found that the
optimum nucleosynthesis yields computed using our diffusion coefficients shift
to longer distance scales by a factor of about 3. We also find that the minimum
value of $^4 He$ abundance decreases by $\Delta Y_p \simeq 0.01$ while $D$ and
$^7 Li$ increase. Effects of these results on constraints from primordial
nucleosynthesis are discussed. In particular, we find that a large baryonic
contribution to the closure density ($\Omega_b h_{50}^{2} \lsim 0.4$) may be
allowed in inhomogeneous models corrected for finite temperature.
