  We point out that the decay mode D^0 -> K^0 \bar{K^0} has no factorizable
contribution. In the chiral perturbation language, treating D^0 as heavy, the
O(p) contribution is zero. We calculate the nonfactorizable chiral loop
contributions of order O(p^3). Then, we use a heavy-light type chiral quark
model to calculate nonfactorizable tree level terms, also of order O(p^3),
proportional to the gluon condensate. We find that both the chiral loops and
the gluon condensate contributions are of the same order of magnitude as the
experimental amplitude.
