  We report an observation of the decay B0 -> D*- tau+ nu and a search for the
rare decays B -> h(*) nu nubar\ove, where h(*) stands for a light meson. A data
sample of 535 million BBbar pairs collected with the Belle detector at the KEKB
e+e- collider is used. We find a signal with a significance of 5.2 standard
deviations on B0 -> D*- tau+ nu and measure the branching fraction to be 2.02
+0.40/-0.37 (stat.) +- 0.37 (syst.)%. No significant signal is observed for B
-> h(*) nu nubar decays and we set upper limits on the branching fractions at
90% confidence level. The limits on B0 -> K*0 nu nubar and B+ -> K+ nu nubar
decays are more stringent than the previous constraints, while the first
searches for B0 -> K0 nu nubar, pi0 nu nubar, rho0 nu nubar, phi nu nubar and
B+ -> K*+ nu nubar, rho+ nu nubar are presented.
