  A quantum-mechanical stability analysis of metallic nanowires within the
free-electron model is presented. The stability is determined by an interplay
of electron-shell effects, the Rayleigh instability due to surface tension, and
the Peierls instability. Although the latter effect limits the maximum length
also for wires with "magic radii", it is found that nanowires in the micrometer
range can be stable at room temperature.
