  We analyze proton decay via dimension six operators in certain GUT-like
models derived from Type IIA orientifolds with $D6$-branes. The amplitude is
parametrically enhanced by a factor of $\alpha_{GUT}^{-1/3}$ relative to the
coresponding result in four-dimensional GUT's. Nonetheless, even assuming a
plausible enhancement from the threshold corrections, we find little overall
enhancement of the proton decay rate from dimension six operators, so that the
predicted lifetime from this mechanism remains close to $10^{36}$ years.
