Evidence against manifest right-handed currents in neutron beta decay

Bounds and presence of manifest right handed currents in neutron beta decay are reviewed. Assuming the unitarity of the Cabibbo-Kobayashi-Maskawa matrix, current experimental situation imposes very stringent limits on the mixing angle, $-0.00077<\zeta<0.00089$, and on the mass eigenstate, $M_2({\rm GeV})\in(291.4,439.9)$, in contradiction with the established lower bound on $M_2$.