The progress of catalytic decomposition of NO (and N2O) and selective catalytic reduction of NO by hydrocarbons in the presence of excess oxygen in the past year (1994) have been summarized. There are many reports and suggestions for the active catalysts and the reaction mechanisms in both reaction systems. Several problems, however, remain to be solved at present; for example, enhancement of the catalytic activity, improvement of the life time, suppression of the formation of the harmful by-products and clarification of the reaction mechanisms.