In this study, the flow properties and dieswell ratios (B's) of two kinds of rubber compounds (SI was a calcium carbonate filled natural rubber compound, and SII was a carbon-black-filled natural rubber/butadiene-styrene rubber/cis-1,4-butadiene rubber compound) in a short-tube extrusion flow were measured by means of a capillary rheometer under test conditions with a temperature of 90 degrees C and an apparent shear rate varying from 10 to 4000 s(-1) to identify the effects of extrusion conditions on the rheological behavior of the materials and to estimate B. The shear flow roughly obeyed the power law, whereas B increased nonlinearly with increasing extrusion rate. Under the same shear rates, the viscosity of SII was higher than that of SI, whereas the values of B of SI were higher than those of SII. Furthermore, B of the rubber compounds was estimated by means of an extrudate swell equation published in a previous work. The results show that the predictions of B were close to the measured data from the experiments. (c) 2007 Wiley Periodicals, Inc.