Latex interpenetrating polymer networks based on high styrene resin ("HSR300") as seed latex and polystyrene as the second polymer have been synthesized in different compositional ratios. The morphology of resultant materials was determined by field emission electron microscopy, atomic force microscopy, transmission electron microscopy, and by dynamic mechanical analysis. A polystyrene (PS) rich shell is observed in the latex particles. At higher second polymer ratios, a PS-rich shell can be resolved, but in general the majority of the polymer is incorporated as domains within each particle. The two crosslinked polymers are well intermeshed at the microscopic level, as reflected not only by morphology but also by single tan delta peaks in dynamic mechanical analysis (DMA) data.