  We present an isospin analysis of the decay modes B\to D\bar{D}, D^*\bar{D},
D\bar{D}^* and D^*\bar{D}^*, which allows determination of the final-state
interaction phases. As these transitions have branching ratios of the order
10^{-4} or larger, they could be useful in detecting the CP- violating phase
\phi_1 \equiv \arg (-V^*_{cb} V_{cd} V_{tb} V^*_{td} ) in the first-round
experiments of a B-meson factory. The problem of penguin pollution may still be
present. Once the Kobayashi-Maskawa matrix elements are known, it is possible
to obtain the magnitudes and relative phases of hadronic matrix elements for
B\to D^{(*)}\bar{D}^{(*)}. This will in turn lead to some information about the
penguin pollution.
