A system is described for stabilizing a cw dye laser frequency to a high‐finesse optical cavity. The length of this optical cavity is locked to a CH4‐stabilized He‐Ne laser with a tunable frequency‐offset technique. A very fast servo system using an intracavity KD*P crystal), a long dye laser cavity, and the stabilized optical cavity result in an absolute frequency stability of 1 kHz for an integration time of 10−4sec and 300 Hz for 300 sec. Intensity is stabilized to one part in 104.