Hydroxyl radical (OH) is measured using laser induced fluorescence in reduced pressure, on-premixed, opposed flow CH4/air flames inhibited by either N-2, CF3Br, or Fe(CO)(5). Emission spectroscopy is used to qualitatively monitor OH for each inhibited flame as well as to characterize the structure of a Fe(CO)(5) inhibited flame. For the flames to which CF3Br and Fe(CO)(5)are added, the OH population decreases approximately proportional to the amount of inhibitor agent added. OH populations decrease faster for flames inhibited by Fe(CO)5 than for flames inhibited by CF3Br.