The nature and wash durability of the cationic fixing agent Matexil FC-ER applied to Tencel fabric, at pH 6 and 11, respectively, was investigated by X-ray Photoelectron Spectroscopy (XPS). The N(1s) XPS spectrum of the Matexil FC-ER film indicated that the concentration of uncharged and quaternary nitrogen species was in the ratio of 5:1. For both pH 6 and pH 11 applications, the surface concentration of the cationic fixative appeared to be independent of pH and the relative proportion of cationic nitrogen relative to the original film, increased at the fibre surface. The ISO 105 CO6/C2S wash test removes the uncharged nitrogen from the fibre surface leaving only the cationic nitrogen species. The surface Matexil FC-ER was durable to washing, while in contrast a direct dye applied to the Tencel fibre was not. Combination with the cationic fixing agent increased the fastness of the dye at the Tencel fibre surface. (C) 2003 Kluwer Academic Publishers.