Using an airborne mounted UV tunable laser system, natural tropospheric OH radical concentrations at 7 and 11.5 km are here reported for the first time. The technique employed was that of Laser Induced Fluorescence where the OH radicals were excited at 2820.6¿ with the fluorescence being monitored at ~3095¿. Sampling of the OH was carried out continuously using a laminar flow intake manifold in which the UV laser beam (7mm diameter) was passed through the center core of the gas stream. Measurements at 32¿ north latitude and 21¿ north latitude at 7 and 11.5 km revealed significant latitude and altitude variations of the OH radical during the month of October 1975. Details on the importance of these measurements to tropospheric chemistry are discussed.