  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
$M_2$.
