  We consider an $SU(3)_L\otimes U(1)_N$ model for the electroweak interactions
which includes extra charged leptons which do not mix with the known leptons.
These new leptons couple to $Z^0$ only through vector currents. We consider
constraints on the mass of one of these leptons coming from the $Z^0$-width and
from the muon $(g-2)$ factor. The last one is less restrictive than the former.
