Chromia-titania interfaces suitable for catalytic application were prepared by repeated chemical reaction (grafting) of Cr(III) amides and Cr(VI) alkoxides with surface hydroxyl groups of TiO2. Their structure, chemical reactions, and redox stability under mild conditions (293-673 K; O-2, air, N-2, H2O/N-2, H-2, NO/NH3) were investigated by EPR, UV-vis (diffuse reflectance), and IR spectroscopy. The conditions necessary to remove residual organic ligands were determined by temperature-programmed oxidation and hydrolysis monitored by mass spectrometry. Polynuclear surface complexes of Cr(III) were obtained by treatment in vacuum or hydrolysis in a H2O/N-2 stream at T < 673 K. The spectroscopic features of these species indicate that highly dispersed chromium oxide species were formed. Calcination in oxygen yields simultaneously Cr(III), (Cr(IV)), Cr(V), and Cr(VI) surface species dependent on the chromium content. All surface species with oxidation states higher than +3 were reversibly reduced by hydrogen to Cr(III). Redox cycles foster the incorporation of Cr(III) ions into the titania lattice. Precursor chromium concentration as well as the conditions applied were found to be decisive for the structural and chemical properties of the immobilized CrOx species. This is also reflected by the catalytic activity and selectivity to Nz in the selective reduction of NO by NH3, which depended on the conditions applied for the sample pretreatment.