Due to development and availability of repositories in different domains, it is becoming difficult for end users to search those repositories comprehensively that provide scholarly materials freely as they need to move from one repository to another that calls for the need to learn retrieval techniques and search operators in use in different repository software systems. This situation calls for the development of a single window search service covering all the repositories in a given domain of knowledge. The above scenario is tried to be solved by metadata integration. Similarity, other areas of scholarship like unique identifiers for resources and contributors, exchange of complex digital resources, sharing of data related to usage of open access resources etc require exchange frameworks and standards and to achieve this potential, we need interoperability.As the situation stands now, the interoperability landscape is presently chaotic and complex as initial dust settlement phase is going on now. This unit attempts to provide you an overview on i) needs, requirements, types and technical issues related to interoperability in open access contents dissemination; ii) present interoperability initiatives; iii) metadata interoperability and harvesting and iv) trends and future possibilities in interoperability.