A continuous flow rheometer based on the principles of helical flow has been developed for measuring the rheological properties of settling slurries. A special feature of the rheometer is its method for data analysis that allows the fundamental rheological parameters to be determined accurately and directly from experimental data without relying on any calibrations. Extensive testing with various fluids and mineral slurries has demonstrated the capability of the instrument for flow property characterisation of complex fluids. A comparison of the results obtained from the helical flow rheometer with those measured independently using a modified tube viscometer and a cone-plate rheometer shows excellent agreement. The numerical procedure developed for data analysis applies to fluids exhibiting any rheological behaviour, including viscoplastic fluids with a yield stress. Particle migration, which is known to affect rheological measurements of particulate systems, is found to have a minimal effect in the rheometer developed. (C) 2003 Elsevier Ltd. All rights reserved.