The oxidation behavior of SiC/porous Al2O3 interphase laminated composites was studied using oxidation experiments and mathematical modeling of the reaction/porous diffusion kinetics in this system. Oxidation at 800 degrees C produced both closure of the interlayer porosity at the lateral ends of the laminate and a limited penetration of the oxidation product layer front from the laminate edges to its interior. Oxidation at 800 degrees C resulted in a persistent product layer of nearly uniform thickness that is more suited to test the effects of oxidation on laminate properties. The modeling approach, which explicitly considers the porous microstructure of the interphase and its evolution upon oxidation, reproduces these experimental observations successfully. The model was extended to study the effect that the mixing of SiC grains with Al2O3 grains to form a two-phase porous interphase has on pore closure at the interface and oxide product front penetration into the interior of the laminate. Pore closure was found to be accelerated considerably with increasing SiC content, and was not accompanied by any significant decrease in the distance from the laminate edges upto which an oxidation product layer was formed.