We have investigated the electronic structure of Sr(Ca)Ru 1− x Cr x O 3 using the full potential linearized augmented plane wave method by different approximation such as LSDA and LSDA+ U. The LSDA calculation suggest that Cr 4+–Ru 4+ hybridization is responsible for the high Curie temperature T C in SrRu 1− x Cr x O 3, but it cannot completely describe its physical behavior. Our LSDA+ U DOS results for SrRu 1− x Cr x O 3 clearly establishes renormalization of the intra-atomic exchange strength at the Ru sites, arising from the Cr–Ru hybridization. The antiferromagnetic coupling of Cr 3+ with Ru 4+,5+ lattice increases the screening, which is consistent with the low magnetic moment of the Ru ions. The more distorted Ca-based compounds as compared to the Sr-based systems shows that the hybridization mechanism is not relevant for these compounds. The bigger exchange splitting of Ru 4 d and Cr 3 d at the Fermi level with Ru 4+,5+ and Cr 3+,4+ orbital occupancies of CaRu 0.75Cr 0.25O 3 in the LSDA+ U calculation, compared with that of the LSDA calculation, shows that repulsion between electrons tend to keep the localized spins from overlapping. The low screening of the Ru t 2 g electrons increases T C in the Ca-based systems, which is consistent with the both high Ru exchange splitting and magnetic moment. The insulating behavior of the high Cr-doped systems can be explained by considering the Ru 4 + + Cr 4 + → Ru 5 + + Cr 3 + charge transfer.