The properties and preliminar applications of porous-silicon (p-Si) microcavities are here reported. These structures are based on a planar resonator formed by two narrow-band high-reflectance distributed Bragg reflectors separated by a thin active optical layer, all of which are made of p-Si layers. The accurate control of the electrochemical dissolution of Si lets us realize p-Si multilayers with the desired refractive indices sequence. Large improvements of the emission properties of p-Si microcavities with respect to standard p-Si samples are observed: 1) increased emission intensity, 2) spectral narrowing of the emission band, and 3) high directionality in the emission pattern. Resonant-cavity light-emitting diodes with higher efficiencies and stabilities with respect to standard p-Si/metal devices are demonstrated. Reflectivity changes due to absorption saturation have been observed.