Flow proper ties of water extract of Roselle calyces were determined using a concentric cylinders rotational viscometer for extract concentration range of 5-65% TS, temperature range of 20-60 degrees C, and shear rate range of 25-979 s(-1). Measured shear stress was within the range 0.5 to 49.7 Pa, corresponding to an apparent viscosity range of 0.0015-1.55 Pa s. Within the rested ranges of concentration, temperature, and shear rate, the extract exhibited a pseudoplastic behaviour, and was adequately described by the simple power law model. The flow behaviour index was consistently below unity (0.76-0.97), with the consistency index varying between 0.007 and 1.6 Pa s(n). Activation energy of flow varied from 18.74 to 42.80 (kJ/kmol) for the extract concentration range of 5-65% TS, at a shear rate of 100 s(-1) The experimental results were fitted by mathematical models to allow prediction of apparent viscosity as a function of concentration, temperature, and shear rate.