This International Standard specifies a method for determining the drawing and break characteristics of molten plastics. The method involves the measurement of the force generated in deforming a molten filament under defined extrusion temperature and drawing conditions. Data is generated under non-isothermal and non-homogeneous deformation conditions. However, it is useful for the interpretation of polymer behaviour in extensional flow. The method is suitable for thermoplastics moulding and extrusion materials that can be extruded using a capillary extrusion rheometer, or an extruder with capillary rod die or other extrusion devices, and have sufficient melt strength to be handled without difficulty. Such materials should be chemically stable and produce a uniform extrudate free from heterogeneities, bubbles, unmelted impurities, etc. This method may provide information on: — processability for all extrusion techniques; — the effect of mechanical and thermal history; — the effect of chemical structure, such as branching, entanglements and molecular mass. This technique is one of a number of techniques that can be used to measure the extensional flow behaviour of a material. This method of measurement does not necessarily reproduce the drawing conditions to which thermoplastics are subjected to during their processing.