  The TWIST experiment has made a precision measurement of three of the decay
parameters in muon decay. The newest results are rho = 0.75014 +-0.00017(stat)
+-0.00044(sys) +-0.00011(eta) and delta = 0.75067 +-0.00030(stat)
+-0.00067(sys). Together with previously published results, improved
constraints on possible extensions of the electroweak Standard Model are
derived.
