  B physics is sensitive to the effects of Higgs bosons in the Minimal
Supersymmetric Standard Model, if the parameter tan beta is large. I briefly
summarise the role of B -> mu+ mu- and B -> tau nu in the hunt for new Higgs
effects and present new results on the decay B -> D tau nu: Using the
analyticity properties of form factors one can predict the ratio R=Br(B -> D
tau nu)/Br(B -> D l nu), l=e,mu, with small hadronic uncertainties. In the
Standard Model one finds R= 0.31 +/- 0.02, Br(B^- -> D^0 tau^- anti-nu) = (0.71
+/- 0.09)% and Br(anti-B^0 -> D^+ tau^- anti-nu)= (0.66 +/- 0.08)%, if the
vector form factor of the Heavy Flavor Averaging Group is used. B -> D tau nu
is competitive with B -> tau nu in the search for effects of charged Higgs
bosons. Especially sensitive to the latter is the differential distribution in
the decay chain anti-B -> D anti-nu tau^-[->pi- nu].
