We report high‐efficiency high‐power uv generation at 266 nm by frequency quadrupling of Nd laser using two deuterated KDP crystals. An angle‐tuned type‐II phase‐matched (eoe‐interaction) deuterated KDP crystal is used for doubling 1.064 &mgr;m and a temperature‐tuned 90° phase‐matched deuterated KDP crystal is used, for the first time, for doubling 532 nm to 266 nm. Results indicate that an average uv power of several watts with an over‐all quadrupling efficiency of around 20% is obtainable, and that high peak uv power on the order of 10 GW with an efficiency of greater than 35% can be expected for subnanosecond pulses. The high peak uv power is potentially useful for fusion studies.