This work describes the adaptation of a temperature-programmed reaction (TPRe) analysis to determine the effective titania surface area (ETSA) in mixed titania/silica catalysts used for the selective catalytic reduction of nitrogen oxides. Isopropanol is used as the probe molecule. Since dehydration of the alcohol adsorbed on the titanyl and silanol groups occurs at two distinct temperatures, the exposed (or effective) titania surface area can be measured through quantitation of evolved propene over the titanyl,stoups via mass spectrometry. Relevance of the use of this technique in the evaluation of raw powders and finished monoliths prior to active metal impregnation is demonstrated through comparison of ETSA data to catalyst activity data with good results.