Dynamic Scaling near Bicritical Points

We calculate by renormalized field theory, up to two-loop order, the bicritical dynamic exponents of stochastic models appropriate for describing spin-flop bicritical points. In the presence of reversible mode-coupling terms, two-loop contributions establish bicritical dynamic scaling in the restricted sense and invalidate recent predictions based on mode-coupling arguments. In case of a purely relaxational model, total bicritical dynamic scaling is found to second order in $\epsilon =4-d$.