An experiment to search for the T-violating transverse muon polarization inK+→&mgr;+&pgr;0&ngr;&mgr;decay(K&mgr;3+)is now underway at the KEK 12 GeV proton synchrotron in Japan. The experiment uses a stoppedK+beam and a large Superconducting Toroidal Spectrometer. The expected limit onP&mgr;⊥will set constraints on non-standard models of CP-violation such as the multi-Higgs doublet model. The experiment should finish data-taking by the end of 2000. ©2000 American Institute of Physics.