Metal-support interaction effects and their consequences in CO2/CO methanation and methane steam reforming have been exemplarily studied on two complex Ni-perovskite powder catalyst systems, namely Ni-La0.6Sr0.4FeO3-delta (lanthanum strontium ferrite, LSF) and Ni-SrTi0.7Fe0.3O3-delta,5 (strontium titanium ferrite, STF). Pre-reduction in hydrogen and treatment in catalytic gas mixtures cause a variety of structural effects, including exsolution of iron particles and formation of Ni-Fe alloy particles. These manifestations strongly depend on the reducibility of the perovskite and are hence much more pronounced on LSF. Reactivity differences are strongly influenced by the chemical properties of the respective perovskite support. The more reducible the perovskite support, the stronger the deviation from the catalytic behavior of a Ni/Al2O3 reference catalyst, rendering establishments of direct structure-activity/selectivity relationships difficult. The studies show the extreme variety of the metal-perovskite interface, which helps in judging similar systems of recent high catalytic importance, e.g. metals supported on spinel or other perovskite phases. (C) 2016 Elsevier Inc. All rights reserved.