Abstract:In eight samples of organic and organomineral surface horizons we studied the stability of soil organic matter in aerobic and anaerobic conditions expressed by the rate constant of its biochemical oxidation, total biochemical oxygen demand, substrate production of methane and degradability in anaerobic conditions. In the eight very different samples no relationship was found between aerobic and anaerobic stability of their organic matter; nor was the expected relationship between total biochemical oxygen demand and "active carbon" C hws proved. Methods of determination are described.