Purpose - The purpose of this paper is to describe the activities of Bielefeld University Library in establishing OAI based repository servers and in using OAI resources for end-user-oriented search services like Bielefeld Academic Search Engine (BASE). Design/methodology/approach - Discusses OAI based repository servers. Findings - BASE is able to integrate external functions of Google Scholar. The search engine technology can replace or amend the search functions of a given repository software. BASE can also be embedded in external repository environments. Originality/value - The paper provides an overview of the functionalities of BASE and gives insight into the challenges that have to be faced when harvesting and integrating resources from multiple OAI servers.