  We study potential New Physics effects in the $\bar B \to D^{(*)} \tau
\bar\nu$ decays. As a particular example of New Physics models we consider the
class of leptoquark models and put the constraints on the leptoquark couplings
using the recently measured ratios $R(D^{(*)})=BR(\bar B \to D^{(*)} \tau
\bar\nu)/BR(\bar B \to D^{(*)} \mu \bar\nu)$. For consistency, some of the
constraints are compared with the ones coming from the current experimental
bound on $BR(B \to X_s \nu \bar\nu)$. In order to discriminate various New
Physics scenarios, we examine the correlations between different observables
that can be measured in future.
