NO adsorption on a Pt(100)-(hex) surface and NO(ads) reaction with hydrogen at 300 K have been studied by HREELS, LEED, TDS and isothermal desorption. NO adsorbs in molecular form, its molecules gathering in islands with a high local coverage. Surface reconstruction into a (1 x 1) phase proceeds within the boundaries of islands. Reaction NO + H2 is performed via NO(ads) previous heating in vacuum at T(h) = 375-425 K. Kinetics of NO(ads) titration appears to be autocatalytic. Nitrogen is the major reaction product.