  Present measurements of b->c tau nu and b->u tau nu transitions differ from
the standard model predictions of lepton flavor universality by almost 4sigma.
We examine new physics interpretations of this anomaly. An effective field
theory analysis shows that minimal flavor violating models are not preferred as
an explanation, but are also not yet excluded. Allowing for general flavor
violation, right-right vector and right-left scalar quark currents are
identified as viable candidates. We discuss explicit examples of two Higgs
doublet models, leptoquarks as well as quark and lepton compositeness. Finally,
implications for LHC searches and future measurements at the (super)B-
factories are presented.
