The problem is analysed of coordination of time relations between demand for final products on one hand and the need for resources, semiproducts and other components on the other one. In this respect we present MRP (Material requirements planning) methods that are applicable in the case of the deterministic demand for final products. Practical use of the mathematical models faces the problem of available data for models. In many situations it is difficult to accurately estimate holding and shortage costs. The work describes a procedure enabling both to approximate data and to analyse possibilities of efficiency improvement of the existing inventory policy. Finally, the JIT system (Just in Time Production) and its implementation in EOQ environment is presented.