  We examine the phenomenology of a low-energy extension of the Standard Model,
based on the gauge group SU(3) x SU(2) x U(1) x SO(3), with SO(3) operating in
the shadow sector. This model offers $\nu_{e} \to \nu_{s}$ and $\nu_{\mu} \to
\nu_{\tau}$ oscillations as the solution of the solar and atmospheric neutrino
problems. Moreover, it provides a neutral heavy shadow lepton X that could play
the role of a cold dark matter particle.
