  We have theoretically investigated the influence of interface roughness
scattering on the low temperature mobility of electrons in quantum wires when
electrons fill one or many subbands. We find the Drude conductance of the wire
with length $\mathcal{L}$ first increases with increasing linear concentration
of electrons $\eta$ and then decreases at larger concentrations. For small
radius $R$ of the wire with length $\mathcal{L}$ the peak of the conductance
$G_{max}$ is below $e^2/h$ so that electrons are localized. The height of this
peak grows as a large power of $R$, so that at large $R$ the conductance
$G_{max}$ exceeds $e^2/h$ and a window of concentrations with delocalized
states (which we call the metallic window) opens around the peak. Thus, we
predict an insulator-metal-insulator transition with increasing concentration
for large enough $R$. Furthermore, we show that the metallic domain can be
sub-divided into three smaller domains: 1) single-subband ballistic conductor,
2) many-subband ballistic conductor 3) diffusive metal, and use our results to
estimate the conductance in these domains. Finally we estimate the critical
value of $R_c(\mathcal{L})$ at which the metallic window opens for a given
length $\mathcal{L}$ and find it to be in reasonable agreement with experiment.
