  We present a measurement of the branching fraction for the semileptonic B
decay Bbar -> D+l-nubar, where l- can be either an electron or a muon. We find
Gamma(Bbar -> D+l-nubar)= (13.79+/-0.76+/-2.51) ns^{-1}, and the resulting
branching fraction Br(Bbar -> D+l-nubar)= (2.13 +/- 0.12 +/- 0.39)%, where the
first error is statistical and the second systematic. We also investigate the
Bbar -> D+l-nubar form factor and the implications of the result for |Vcb|.
  From a fit to the differential decay distribution we obtain the rate
normalization |Vcb|F_D(1)= (4.11+/-0.44+/-0.52)x10^{-2}. Using a theoretical
calculation of F_D(1), the Cabibbo-Kobayashi-Maskawa matrix element
|Vcb|=(4.19+/-0.45+/-0.53+/-0.30)x10^{-2} is obtained, where the last error
comes from the theoretical uncertainty of F_D(1). The results are based on a
data sample of 10.2 fb^{-1} recorded at the Upsilon(4S)$ resonance with the
Belle detector at the KEKB e+e- collider.
