Results from a surface study of titania-supported cobalt are presented. The data show a clear interaction between the Ti(110) support and the overlayer, as a function of thermal treatments and oxidation state. Two model substrates, fully oxidized and partially reduced TiO2, were impregnated with metallic cobalt or cobalt oxide via dry chemical methods. The resulting four combinations, TiO2-o/Co, TiO2-o/CoO, TiO2-r/Co, and TiO2-r/CoO, were compared with reference spectra for the isolated constituents by means of electron spectroscopic measurements following annealing to subsequently higher temperatures. We employ a new "fingerprint" technique to analyze the data, thereby allowing us to utilize all available peak positions for a better understanding of chemical interactions and dispersion changes. From our data we can conclude that only metallic cobalt influences the chemical state of titania. The dispersion of CoO changes at moderate temperatures, 500-700 K, but this is restricted to coalescence of the overlayer. The overlayer oxide is less stable on the partially reduced support than on fully oxidized titania. Metallic cobalt, as deposited or from decomposition of CoO, diffuses into titania at above 700 K on TiO2-o and : above 500 K on TiO2-r. This interdiffusion is accompanied by a reduction of the support. The lower stability of CoO on the partially reduced support is accompanied by a stabilization of cobalt in the surface region and we conclude that the driving force for the destabilization may be the formation of a bimetallic coating. This anomalous stabilization of Co near the surface is only observed for thick overlayers of cobalt metal on oxidized titania and for CoO on TiO2-r.