First-principles (ab-initio) calculations allow studies of properties of solids on the fundamental level. The electronic structure determines most physical properties of a solid. Such calculations became enormously enhanced by Density Functional Theory (D FT). They involve crystal structure data obtained experimentally and do not rely on empirical inputs. One becomes thereby able to predict many physical properties accurately, thereby helping chemistry with reducing costs and increasing reliability of expe rimental works. The access to supercomputers and advanced computational methods, facilitates accurate studies of materials with complex crystal structures. The present aim is to study electronic structure, magnetic, magneto-optical (MO) and optical proper ties of perovskite-like oxides with state-of-the-art DFT methods. The main objectives are: 1. Spin, charge and orbital ordering is important to most CMR materials and is believed to result from mixed valence of magnetic atoms. Electronic band structure studies of mixed-valence materials will help answering fundamental questions related to CMR. 2. Magneto-optical properties connect to spectacular developments in the frontier of information technology where magnetic materials are used as information storage devices and magneresistant sensors. Theoretical investigations of magnetism and MO propert ies such as Farday and Kerr rotation for double perovskite oxides may enable identification of potential materials for information storage applications. 3. Optical properties has a one-to-one correspondence to electronic structure. Moreover, to derive a MO figure-of-merit, reflectivity and absorption spectra are needed. If times allows, the calculations will include optical properties of a series of doubl e perovskites.