Today, the cellulose degree of polymerisation (DP) is generally considered the main parameter for kraft fibre strength prediction. Although various DP/strength correlations have been established in the past, there is no such thing as a unique linear trend encompassing the large diversity of chemicals affecting cellulose integrity. In fact, some chemical treatments would target weak spots in the fibres (ie. kinks or curls). Derivatisation reactions (e.g. carbanilation, etherification) performed without proper swelling or dissolution of the fibres induces incomplete and localised reactions due to inaccessible cellulose domains . Other examples include both acid and enzymatic (cellulase) hydrolyses of cellulosic fibres ). On the contrary, homogeneous degradations like those triggered by alkaline hydrolysis would not substantially decrease fibre strength despite a critical DP loss . Therefore, knowing the homogeneity of cellulose degradation both at the macro and ultrastructure levels would be key to predict fibre strength loss, and not solely the average carbohydrates DP commonly measured as the pulp viscosity dissolved in Cuen (DPv) (Figure ). Discriminating homogeneous and heterogeneous/localised degradation patterns is not an easy task. Heterogeneous degradations encompass localised degradations affecting specific parts of the fibresusually local defects -and degradations selective towards specific cell wall layers or cellulose chains lengths. Cellulase enzymes and acid hydrolysis fall in the first category ) whereas treatments such as sonication would preferentially affect long cellulose chains . A sure fact is that the DPv gives no information on the topochemistry of cellulose degradation occurring within the fibres. Alternatively, Size Exclusion Chromatography (SEC) seems more relevant when dealing with pulp chemical degradations ). For hardwood pulps, the now widely-used method for SEC is the direct dissolution of fibres in a DMAc/LiCl (8%) mixture . In this work, the direct dissolution method has been favoured over the carbanilation for reasons mentioned above.