We have constructed high-finesse light-emitting microcavities from the conjugated polymer poly(p-phenylene-vinylene), PPV, and high reflectivity distributed Bragg reflectors. The modifications to the photoluminescence and electroluminescence of the polymer arising from confinement of the photon field by these mirrors were investigated. Spontaneous emission enhancements of 2 orders of magnitude were found in the forward direction. The total integrated quantum yield for photoluminescence from PPV in such devices was 8.5 ±1%. Stimulated emission from these devices was also investigated using short-pulse laser excitation. The emission line width narrowed by a factor of 2 above the lasing threshold. Short-term polarisation memory effects were observed as the life time of the excited states were reduced by coupling to stimulated emission. The lasing threshold for pulsed excitation was found to have been reduced by an order of magnitude, to 15 μJ/cm 2 , compared to previous studies on microcavities incorporating metal mirrors. Findings were complemented by simulations of the optical fields using multi-layer stack theory and transfer matrices.