  We calculate the plasmon dispersion in quasi-one-dimensional quantum wires,
in the presence of non-magnetic impurities, taking into consideration the
memory function formalism and the role of the forward scattering. The plasma
frequency is reduced by the presence of impurities. We also calculate,
analytically, the plasmon dispersion in the Born approximation, for the
scattering of the electrons by the non-magnetic impurities. We compare our
result with the numerical results of Sarma and Hwang.
