  We calculate the conductance of a quantum wire with two occupied subbands in
a presence of a barrier taking into account the interaction between electrons.
We extend the renormalization-group equation for the scattering matrix of the
barrier to the case of intersubband interactions, find its fixed points, and
investigate their stability. Depending on the interaction parameters, the
conductance may be equal to 0, $e^2/h$, or $2e^2/h$ per spin projection. In
some parameter ranges, two stable fixed points may coexist, so the ultimate
conductance depends on the properties of the bare barrier. For spinful
electrons, the conductance of the wire may nonmonotonically depend on the Fermi
level and temperature.
