This International Standard describes methods for the preparation of test samples used in the determination of the ultimate aerobic and anaerobic biodegradability of plastic materials in an aqueous medium, soil, controlled compost or anaerobic digesting sludge. The methods described are designed to provide dimensional consistency of test samples, resulting in improved reproducibility of test results during the determination of the ultimate biodegradability of the product. These methods apply to the following materials: natural and/or synthetic polymers, copolymers or mixtures of these; plastic materials that contain additives, such as plasticizers or colorants; plastic composite materials that contain organic or inorganic fillers; products made from the above materials.