  The Yale stellar evolution code has been modified to include the combined
effects of diffusion and rotational mixing on $^1$H, $^4$He and the trace
elements $^3$He, $^6$Li, $^7$Li, and $^9$Be. The interaction between rotational
mixing and diffusion is studied by calculating a number of calibrated solar
models. The rotational mixing inhibits the diffusion in the outer parts of the
models, leading to a decrease in the envelope diffusion by 25 -- 50\%.
Conversely, diffusion leads to gradients in mean molecular weight which can
inhibit the rotational mixing. The degree to which gradients in mean molecular
weight inhibits the rotational mixing is somewhat uncertain. A comparison to
the observed solar oblateness suggests that gradients in the mean molecular
weight play a smaller role in inhibiting the rotational mixing previously
believed. This is reinforced by the fact that the model with the standard value
for the inhibiting effect of mean molecular weight on the rotational mixing
depletes no Li on the main sequence. This is in clear contrast to the
observations. A reduction in the inhibiting effect of mean molecular weight
gradients by a factor of ten leads to noticeable main sequence Li depletion.
