Porous organic and inorganic materials with both random and controlled microstructures have utility in a variety of fields including catalysis, sensors, separations, optical platforms, tissue engineering, hydrogen storage, micro-electronics, medical diagnostics, as well as other applications. This work highlights a simple and general technique for tuning the pore size in crosslinking polymeric systems by adding a solvent poragen that phase separates during the curing process (reaction induced phase separation). The pore size can be controlled over large length scales ranging from microns to well below 100 nanometers. In this system an amine cured epoxy resin was reacted in the presence of the sacrificial poragen octadecanol, which is removed by vacuum-assisted evaporation once the epoxy components have reacted to form a solid, porous matrix. The importance of the present approach is based on the simplicity of the chemical formulation, the ease by which other epoxide or amine chemistries may be substituted for the two reactive components, and the control of pore size down to the nanometer scale by the addition of a small amount of catalyst. (C) 2010 Wiley Periodicals, Inc.(dagger) J Appl Polym Sci 117: 3300-3307, 2010