This International Standard describes methods for the determination of soil microbial respiration of aerobic, unsaturated soils. The methods are suitable for the determination of O2 uptake or CO2 release, either after addition of a substrate (substrate-induced respiration), or without substrate addition (basal respiration). This International Standard is applicable to the measurement of soil respiration in order to:  determine the microbial activity in soil (see [3]);  establish the effect of additives (nutrients, pollutants, soil improvers, etc.) on the metabolic performance of microorganisms;  determine the microbial biomass (see [4]);  determine the metabolic quotient qCO2.