This paper reports recent observations on the performance of continuous ruby lasers and compares them with theoretical computations of threshold, power output, and efficiency. The theoretical model includes effects due to scattering, temperature,2Elevel splitting, and excited‐state absorption. It is used to compute numerically the optimized output coupling for various pump levels and the corresponding power outputs. Experimentally, power outputs of up to 2.4 W and incremental (above threshold) efficiencies of ∼0.11% were observed. Some experiments on the effects of differing crystal diameters and cooling water temperatures and flow rates were performed. Good agreement was obtained between the observed and computed dependence of power output and efficiency on various laser parameters. The agreement is of significance primarily because it implies that the theoretical model can be used in optimizing the design of continuous ruby lasers, and in predicting their performance. Results of rough calculations of projected performance are given.