While IS research into on-line Inter-Personal (IP) Social Networks (SN) is highly visible, there has been surprisingly little focus on the use of on-line social networks for Inter-Organizational (IO) communications, interactions, and goal achievement. We explore the issues and challenges facing organizations in their design and use of inter-organizational social network information systems (IO SNIS). Artifact design principles are drawn from a new and insightful model that contrasts the advantages of existing innovative inter-personal (IP) SNIS artifacts with Social Network Theory on differences between IP and IO Social Networks. This research extends the existing streams of IS social networking research into the inter-organizational domain and encourages additional IS research into the analysis, design, and build of artifacts that animate the social behavior of organizations. We develop a key design concept for IO SNIS and establish the design principles underlying the general artifact design and the specific design features that apply the design constructs to an exemplar IO social domain. This dissertation uses Action Design Research (ADR) approach within the Design Science Research (DSR) paradigm to formulate the research opportunity and anticipate a practice-inspired and theory-ingrained artifact. The researcher works with a practitioner team in the domain of mid-market private equity (MMPE) to explore the model and evaluate existing on-line inter-organizational artifacts to establish specific design features for an IO SNIS artifact. We find that the design principles can generalize from the IO SNIS Design Concept Model to other IO Social domains and that the design features can be used to build an instantiation of IO SNIS in the Private Equity domain.