Evidence against manifest right-handed currents in neutron beta decay

The bounds and presence of manifest right-handed currents in neutron beta decay are reviewed. Assuming the unitarity of the Cabibbo-Kobayashi-Maskawa matrix, the current experimental situation imposes very stringent limits on the mixing angle, -0.000 77 < zeta < 0.000 89, and on the mass eigenstate, M-2 (GeV) is an element of (291.4, 439.9), in contradiction with the established lower bound on M-2.