Charged current couplings in τ decay

We discuss the impact of the recent measurements of the Michel parameter in τ decay. These measurements are used to extract limits on the charged current couplings beyond the Standard Model, first in a model independent way and then with some additional but very general assumptions. The measurements substantiate the Standard Model V-A hypothesis and restrict right handed couplings of the τ. On the other hand, left handed scalar and tensor couplings of the τ channot be bounded in the model independent framework with presently available data. (orig.)