Confocal laser scanning microscopy (CLSM) and three-dimensional (3D) image reconstruction were used to visualize the interconnecting pores that result from the bi-axial stretching of CaCO3/polyolefin composite membranes. The following three effects on pore connectivity were examined: (1) amount of membrane stretching-unstretched, low-stretched, and overstretched; (2) polymer matrices-polyethylene and polypropylene; (3) particle coatings-uncoated CaCO3 (calcite) and stearic acid coated calcite. The porosity of the membranes increased with quantifiable increases in their elongation. The pattern of the interconnecting pores depended on the polymer matrix and the particulate coating, where the change in the pattern was related to the stiffness of the composite material and the nature of the interaction at the polymer/calcite interface. (c) 2005 Elsevier B.V. All rights reserved.