  We present a first measurement of CP asymmetries in neutral B decays to D+D-,
and updated CP asymmetry measurements in decays to D*+D- and D*-D+. We use
fully-reconstructed decays collected in a data sample of (232 +- 3) x 10^6
Y(4S) -> BBbar events in the BABAR detector at the PEP-II asymmetric-energy B
Factory at SLAC. We determine the time-dependent asymmetry parameters to be
S_{D*+D-} = -0.54 +- 0.35 +- 0.07, C_{D*+D-} = 0.09 +- 0.25 +- 0.06, S_{D*-D+}
= -0.29 +- 0.33 +- 0.07, C_{D*-D+} = 0.17 +- 0.24 +- 0.04, S_{D+D-} = -0.29 +-
0.63 +- 0.06, and C_{D+D-} = 0.11 +- 0.35 +- 0.06, where in each case the first
error is statistical and the second error is systematic.
