Web portal Merkur Partner enables the insight into specific business information over the Internet to external users. This paper - case study discusses the integration between web portal Merkur Partner and other information systems in the company Merkur,d.d.. Data which is displayed in the web portal, already exist in other company's information systems, therefore it is useful to integrate these system and increase business efficiency. The interchange of data between the systems is performed automatically, without human intervention. The most important data flows between the systems are article data, orders and inquires, sales promotions, partners and their users data, subcatalogues and contact persons in Merkur. In this paper the major problems of integration of web portal Merkur Partner with other information systems in Merkur are presented. The paper introduces the further development of the solution and organizational measures, needed for efficient web portal management. Key words: web portal, information system integration, business information, trade, B2B