$D \to KK$ decays

The CLEO-c experiment at the CESR $e^+ e^-$ collider has collected 281~pb$^{-1}$ of data at the $\psi(3770)$ resonance. Using this data sample we have studied Cabibbo suppressed decays of $D$ mesons to final states with kaons. We present preliminary results for the branching fractions of the two-body decays $D^0\to K^+ K^-$, $D^0\to K^0_S K^0_S$, and $D^+\to K^+K^0_S$.