The catalytic removal of NH and NH2 free radicals by polycrystalline Pt and Fe has been studied as a function of catalyst temperature by using the laser-induced fluorescence (LIF) technique. Activation energies for removal of NH and NH2 by Pt and Fe have been determined. On Pt, NH2 and NH show a surface poisoning effect due to the accumulation of decomposition products on the surface. NH was found to desorb from Pt at T > 1200 K and from Fe at T > 1000 K from the metal-catalyzed decomposition of NH3. Desorption of NH has also been observed from the reaction of N2 + H2 on Fe at T > 1000 K. No evidence for NH2 desorption from Pt or Fe was found at all temperatures studied.