Melt spinning experiments were carried out to investigate the elongational behavior and fiber morphology of multiphase polymer systems. Materials chosen for study were blends of calcium carbonate-filled polypropylene with general-purpose polystyrene and blends of calcium carbonate-filled polypropylene with high-impact polystyrene. The former is a three-phase system in which the CaCO3 particles are dispersed, and the latter is a four-phase system in which CaCO3 particles are dispersed, together with rubbery butadiene particles. Note that polypropylene is incompatible with the matrix of high-impact polystyrene. The experimental technique described in part I of this series was used to determine the elongational viscosity. With the four-phase system, the apparent elongational viscosity tends to increase as the stretch ratio is increased above a certain critical value which appears to be ca. 25. This transition does not occur with the three-phase system and is attributable to elongation of the suspended rubber particles. The addition of small amounts of HIPS to PP-CaCO3 increases spinnability in general, whereas larger amounts decrease spinnability.