In the last few years computer aided support of production processes increases. The first step in development of such programs was the design of so called enterprise resource planning systems (ERP). These systems support a few processes in company, but they don’t support operative production processes. As a result of many negative aspects so called manufacturing execution Systems (MES) are developed. MES-systems are software systems, which consist of few modules with different functionality to support production processes in real time. As a result of these modules, functionality and used modules are different for each company. MES-systems connects ERP-systems to operative production processes and solve problems in connection with this gap of information. In this text requirements and potentials that can be generated by a MES-system are developed. Actual there is no clear definition for MES-systems in foundries in literature, so that a clear definition has to be found. In order to understand functionality and scope of MES-systems some basic information is given and important modules are mentioned. To be able to generate weak spots, an analysis of entire production process is necessary. The Model for analysis of system boundary used in this text is the so called SIPOC-model. In order to understand the process flow so called flow charts are used to visualize process steps. The given weak spots define requirements on a MES-System in production process of foundry. Establishment of MES-Systems generates potential and improves information flow within production process. It’s very difficult to assess improvement of implementation of a MES–system, but in this case of steel foundry an amount of potentials are given and illustrated.