Studies were carried out to determine the surface charge and total charge of refined softwood high yield kraft pulps at different levels by titration methods. The results showed that the surface charge was highly dependent on the degree of refining. However, the total fibre charge was not affected by refining. The change of the fibre surface charge during refining monitored using ATR-FTIR characteristic bands was within 1700-1300 cm(-1). Reliable PLS1 calibration models could be established to correlate the FTIR spectral data and the surface charge of the refined pulps. (c) 2006 Elsevier Ltd. All rights reserved.