Grossly disordered compounds present considerable challenge to the experimentalist and to the theoretician. Order and disorder in such systems are usually described either from a structural chemist's point of view or from a high-temperature perspective. A structural chemist often describes ordered low-temperature structures in terms of arrangements of different types of polyhedrons. A high-temperature chemist often describes the disordered high-temperature structures in terms of defect equilibria. The pres ent project aims at producing a description of order-disorder in such systems that covers both the low-temperature and the high-temperature behaviour. Order-disorder in grossly non-stoichiometric oxides is described in terms of the redox energetic s and t hrough a description of the structural entities present in the compounds both at low and at high temperatures. The structural entities gives a considerably reduced configurational entropy compared to the ideal case. The present project aims at looking at order-disorder in owides of the type AeTmO<sub>3-d</sub> where Ae is an alkaline-earth metal and Tm a transition metal. Coulometric titration and calorimetry is used to study the energetics experimentally. Finite tem perature configurationally averaged l attice dynamics and novel Monte-Carlo and hybrid Monte-Carlo simulations are used for theoretical studies. The project introdues several new techniques to Norway.