This document specifies the determination of the molar-mass distribution and the average molar mass values Mn (number average) and Mw (weight average) of polymers that are soluble in DMAC (N,N-Dimethylacetamide) by gel permeation chromatography (GPC). NOTE Also known as size exclusion chromatography (SEC). Even though the chromatograms obtained show good repeatability, it is possible that this method cannot be used with certain polymer types because of specific interactions (e.g. adsorption) within the sample/eluent/column system. The conditions specified in this document are not applicable to the GPC analysis of polymer samples with Mw values greater than 106 g/mol and/or polymers with elution limits outside the calibration range (see 7.6 and Annex C). This document includes no correction method (e.g. for the elimination of peak broadening). If absolute molar mass values are required, an absolute method (e.g. membrane osmometry for Mn or light scattering for Mw) can be used.