The viscosity profiles of six commercially available food thickeners (Guarcol (TM), Keltrol (TM), Novartis (TM), Nutricia (TM), QuikThik (TM), and Supercol (TM)) in water and raspberry: cordial were studied in a strain-controlled rheometer at 20 C. The thickened fluids exhibited a shear-thinning behaviour, and their viscosities were not significantly (p > 0.05) affected by holding time up to 24 h. Irrespective of the thickener and dispersing medium, the viscosity increased as the solids content was increased, as did density and yield stress. Rheological models that best fit the flow data of the thickeners in the dispersing media were recommended. At an assumed shear rate of about 50 s(-1) for normal swallowing, predicted and experimental viscosities are not significantly (p > 0.05) different. The recommended models can be used to calculate the weights of the thickener and dispersing medium to achieve a known viscosity of the thickened fluids, match video-fluoroscopy fluids and obtain objective classification of the thickened fluids. (c) 2006 Elsevier Ltd. All rights reserved.