Noting that networks of relationships between individuals and groups form organization-wide patterns that provide both the structure and the means of sustaining an organization, this paper argues that a complete understanding of organizations requires a basic understanding of these networks. Following a brief discussion of the nature of communication networks, the paper describes a model indicating aspects of communication networks that have been and need to be investigated. The described model includes three categories of potential interest: (1) the communication networks themselves, (2) inputs relevant to communication networks, and (3) the relationships between output and communication networks. Following the development of the model, the paper presents a review of communication network research categorized according to the model. (FL)