The alkaline earth oxides of barium, strontium, and calcium have been studied as catalysts for the decomposition of nitric oxide. The low work function characterizing these oxides is liable to favor an electron donor catalytic process which decomposes the nitric oxide molecule. The latter was Used diluted in helium and the concentration was varied between 0.5 and 2.5%. Experiments were carried out at, respectively, 650 ~ 750 ~ and 850~ After passage over the catalyst, nitric and nitrous oxides were found in the gaseous phase, as well as nitrogen and oxygen. Within the limits of concentrations used, it was found that the decomposition reaction rates of nitric and nitrous oxides are mutually independent. Reaction rate constants were calculated, showing that constants related to nitric oxide were at ]east one' order of magnitude higher than those related to nitrous oxide this explaining, within the limits of concentrations used, the independent behavior mentioned. The total conversion for nitric oxide was highest for barium oxide, attaining 80% at 850~ followed by strontium and calcium oxides. Increasing efficiencies coincide with a decrease in work function. Within the limits of nitric oxide used, up to 3% oxygen do not show any inhibitive effect on nitric oxide decomposition. This may be attributed to a large equilibrium constant for oxygen desorption.Nitric oxide is well known as an air pollutant, the main sources being urban domestic heating during winter and automobile exhaust gases. The role of this oxide~in the photochemical processes occurring during urban atmospheric smog conditions has been well described (1) and a large number of studies have been made on the subject of nitric oxide pollution abatement. Some years ago, the decomposition of nitrous oxide (2, 3) was investigated on various metallic oxides, while more recently extensive research was carried out in relationship with the decomposition of nitric oxide in the presence of metallic oxides (4-6), the associated problem of oxygen inhibition al~o receiving much attention (7, 8). However, most of these oxides, whether considered for the decomposition of nitrous or nitric oxides, do not seem to fulfill the requirements of a suitable catalyst, the main drawback being the slow nitrogen oxides decomposition reaction rate. In this respect, oxygen seems to have a pronounced inhibitive effect in the process of nitrogen oxides catalytic decomposition on metallic oxides. Recently, an interesting method was reported (9), where catalytic decomposition of nitric oxide was performed on zircon/a, while the oxygen produced (an inhibitor in this case) was electrolytically removed from the catalyst's surface.The catalytic decomposition of nitric or nitrous oxides over metallic oxides involves, in most cases, the partial or total rupture of the gas molecule by means of an electron donor type catalytic process. In this respect, metallic oxides with a low work function should deserve some further attention, the alkaline earth oxides being typical examples for this catego...