The extrudate swell behavior and extrudate texture of various thermoplastic melts, namely, polystyrene (PS), low-density polyethylene (LDPE), acrylonitrile-butadiene styrene (ABS) copolymer, poly(vinyl chloride) (PVC), and their blends, were examined weith a magnetic die system in a constant-shear-rate capillary rheometer at a shear rate range 5-28 s(-1) and a temperature range 170-230 degreesC. The extrudate swell results obtained from the magnetic die were then compared with those produced by a nonmagnetic die. The results showed that the extrudate swell increased with shear rate, but decreased with temperature. In a pure polymer system, up to 25% increase in the extrudate swell was observed with the application of the magnetic field to the PS melt, and the effect decreased in the order ABS > LDPE > PVC. The extrudate swell changes were associated with the changes in rheological properties of the melts. The extruclate textures of the ABS and PVC melts were improved by the magnetic field. In PS/LDPE or PS/ABS blend, it was found that the magnetic die resulted in higher values of the extruclate swell than the nonmagnetic die for all blends, the magnetic effect being less as the LDPE or ABS content was increased. For PS/LDPE system, the extruclate swell of the PS melt did not change much with addition of 20% LDPE, but slightly decreased at the LDPE loading of 40%. At higher LDPE loadings, the extruclate swell increased towards the value of the pure LDPE melt. For PS/ABS system, the extruclate swell ratio progressively decreased with increasing ABS content.