  Inclusive branching ratios involving b to tau transitions are measured in
approximately four million hadronic Z decays collected by the ALEPH detector at
LEP. The fully-inclusive branching ratio b -> tau nu X and the semi-inclusive
branching ratio b -> tau nu D*+/- X are measured to be (2.43 +/- 0.20 +/-
0.25)% and (0.88 +/- 0.31 +/- 0.28)%, in agreement with the standard model
predictions. Upper limits on the branching fractions b -> tau nu and b -> s nu
nubar are set to 8.3 10**-4 and 6.4 10**-4 at the 90% C.L. These results allow
a 90% C.L. lower limit of 0.40 (GeV/c**2)**-1 to be set on the tan(beta)/mH+/-
ratio, in the framework of type-II two-Higgs-doublet mode
