ISO 10640:2011 provides a methodology to assess the ageing of polymeric systems during exposure to laboratory accelerated weathering as well as in outdoor exposures. This methodology applies mainly to photoageing, but it can also be applied to thermal ageing. The methodology identifies analyses that follow the chemical changes which control the deterioration of physical properties of materials during photoageing. The main procedure is based on IR spectroscopy analysis and is described in the standard. In addition, UV spectroscopy is used for monitoring the behaviour of some additives and to identify the origin of discoloration in polymeric materials (degradation of pigments and colorants, or polymer yellowing). Examples of applications of this methodology are given in an annex as guidance for the interpretation of the results.