The theoretical power output of a ruby laser is examined under certain idealized operating conditions, and it is found that there are two principal regions of operation. These are the regions of strong oscillation characterized by the conditionp&tgr;2/A»h&ngr;13/&sgr;13and the region of saturation in whichp&tgr;3/A»h&ngr;13/&sgr;13. Herep/Ais the ``pumping'' illumination within the absorption band of ruby, &tgr;2is a charactersitic relaxation time of fluorescence in ruby, &tgr;3is a characteristic thermal relaxation time from the excitedUband, &ngr;13is the pumping frequency, and &sgr;13is the cross section for interaction between pumping radiation and Cr3+ions in ruby. Efficiency of operation is examined under two limiting conditions.