The characteristics of photonic crystal microcavity light sources are presented. Microcavities with dimensions on the scale of the wavelength of light are extensively investigated due to their ability to exhibit enhanced spontaneous emission, directional output, and single-mode operation. Thus, it is believed that electrically injected photonic crystal microcavity light sources may realize high-efficiency single-mode LEDs. Electrically injected microcavities offer the advantage of possible integration with current optoelectronic circuits and devices. Moreover, arrays of such devices can be fabricated when electrically controlled.