  We demonstrate polarization spectroscopy of an excited state transition in
room temperature cesium vapor. An anisotropy induced by a circularly polarized
pump beam on the D2 transition is observed using a weak probe on the 6P3/2 to
7S1/2 transition. When the D2 transition is saturated, a sub-natural linewidth
feature is observed which theoretical modeling shows is enhanced by Doppler
averaging. Polarization spectroscopy provides a simple modulation-free signal
suitable for laser frequency stabilization to excited state transitions.
