A broad range of Inter-Organizational Decision Support Systems (IODSSs) can be built to support external stakeholders of an organization. This article examines recent developments associated with building and deploying such systems. The IODSS concept is defined, and an information technology architecture for such a system is explored. Examples of current implementations are categorized as communication, data, document, knowledge, and model-driven IODSSs. Further, implementations of IODSSs are categorized as customer- and supplier-focused. Advantages, disadvantages, and current issues associated with IODSSs conclude the discussion.