Batches of 100 g unbeaten, bleached softwood sulphite fibres dispersed in 20 1 distilled water were prepared and mixed with increasing amounts of a commercial filler grade of titanium dioxide. The addition level ranged from 0.5 to 3.0 g TiO₂/g fibres. Each mixture was stirred slowly for 1 h with a blade stirrer (40 rpm) to prevent sedimentation. After this time the adsorption equilibrium was established. Four samples, 100 ml each, of the supernatant liquid were drawn with a plastic tube covered with a fine wire mesh at the bottom. From the TiO₂ content of the samples the amounts of TiO₂ adsorbed on the fibres were calculated.