Profile measurements in a catalytic gauze reactor are conducted for catalytically assisted methane combustion over platinum. The reactor combines a capillary sampling technique with a novel fiber-optic laser-induced fluorescence spectroscopy method for the detection and quantification of gas phase OH. radicals serving as indicator species for gas phase reactions. Experimental profiles are compared with three-dimensional numerical reactor simulations including flow, mass transport, heat transport, and microkinetic models for both surface and gas phase chemistry. The results provide insights into the interaction of chemistry and transport upstream of, at, and downstream of the catalytic gauze, and the interaction of surface and gas phase reactions by exchange of heat and radicals released from the catalyst surface.