  Electron-positron annihilation data collected by the BABAR detector near the
Y(4S) resonance are used to study the inclusive decay of B mesons to D_S^(+/-)
and D_S^(*+/-) mesons, where the D_S^(+/-) is reconstructed using the decay
D_S^(+/-) --> phi pi^(+/-). The production fraction of inclusive D_S^((*)+/-)
and the corresponding momentum spectra have been determined. The exclusive
decays B^0 --> D^(*-)D_S^((*)+) are observed with a partial reconstruction
technique which uses the soft pion from the D^(*+/-) decay in association with
the reconstructed D_S^((*)+/-). The beam energy constraint is used to determine
the missing mass recoiling against the D_S^(+/-) system, showing a clear signal
for this process. From the observed rates, preliminary results for the
corresponding branching fractions have been obtained.
