Inoculant biofertilisers are preparations that contain beneficial micro-organisms that are applied to crops with the aim of reducing or replacing more costly and environmentally damaging chemical fertilisers. Research has shown that rice yields in Vietnam can be maintained and even increased with reduced application rates of chemical fertiliser when treated with the biofertiliser BioGro. However, the benefits of reduced input costs and potential yield increases can only be achieved if there is adequate quality control of biofertiliser production. This manual provides a set of guidelines for the routine testing of biofertiliser quality. The methods chosen seek a balance between the use of modern technologies and the needs of developing countries with limited resources other than labour.