The lack of adequate characterization techniques has been a hindrance to the effective exploitation and study of co-continuous morphologies in polymer blends. In this paper we prepare co-continuous blends of high density polyethylene/polystyrene in order to compare Various microstructural characterization techniques. The influence of a triblock copolymer interfacial modifier, hydrogenated styrene-ethylene-butadiene-styrene on the system has also been investigated The surface area and pore dimensions of the blend system after solvent extraction of one of the phases have been measured using the BET nitrogen adsorption technique and mercury porosimetry, respectively. Image analysis was also carried out as a third source of microstructural information. It is shown that mercury porosimetry can lead to erroneous information while the BET method appears to be both rapid and consistent with SEM observation. The specific surface area of the compatibilized co-continuous blend system is five fold higher than that of its non-compatibilized counterpart, while the pore diameter of the extracted compatibilized blend is reduced five fold. Using the BET technique, it is possible to generate an emulsification curve in the continuous region, demonstrating the efficacy of the interfacial modifier in this complex system. (C) 2001 Elsevier Science Ltd. All rights reserved.