The OH number density in the stratosphere has been measured over the altitude interval of 37 to 23 km at midday via a balloon-borne gondola launched from Palestine, Texas on July 6, 1988. OH radicals are detected with a laser induced fluorescence instrument employing a 17 kHz repetition rate copper vapor laser pumped dye laser optically coupled to an enclosed flow, in situ sampling chamber. OH abundances ranged from 88¿31 pptv (1.1¿0.4¿107 molec cm-3) in the 36 to 35 km interval to 0.9¿0.8 pptv (8.7¿7.7¿105 molec cm-3) in the 24 to 23 interval. The stated uncertainty (¿1&sgr;) includes that from both measurement precision and accuracy. Simultaneous detection of ozone and water vapor densities was carried out with separate on-board instruments. ¿ American Geophysical Union 1989