A model aqueous injection moulding paste was investigated by capillary theology. The experimental work consisted of 26 pressure measurements on each of three capillaries to provide an extended shear rate range from 0.5 to 150 s(-1). A power law model was found to be adequate for general prediction of the flow curve. However, slip flow had to be taken into account to map the shape of the flow curve more accurately. The Hatzikiriakos method, which does not require the use of different diameter capillaries, was applied to measure slip flow and gave rational solutions. The flow curve was modelled using rheological parameters for shear how and slip flow over the region of the flow curve for which they were valid. The adjusted model incorporating slip flow gave a better correlation with the experimental results.