This paper discusses a typology and evaluations of inter-firm relationships in the telecommunications industry. The authors define inter-firm relationships as a broad range of relationships including strategic alliances, joint ventures, and mergers and acquisitions (M&A) or other equity-based relationships. Forming relationships and selecting partners are the two most important issues for managers when arranging inter-firm relationships and these are also important subjects for research in this area. The authors empirically analyzed inter-firm relationships by evaluating short-term stock-market responses to announcements about the formation of such relationships. These evaluations follow typologies previously proposed by the authors, which are explained in this paper. Three hypotheses are proposed and examined regarding general market responses and the difference in responses between each defined type of relationship and market.The results from evaluations revealed that market responses were generally not favorable in the short term in contrast to general understanding of market responses. However, the authors found significant differences in responses between the relationship categories of the framework. Practical implementations were obtained where managers in the industry had to take into account how the stock market responded to the formation of inter-firm relationships when they developed their corporate strategies. The results also demonstrated the validity of the proposed framework and suggested it should be useful to enable further analysis of this industry. Yoshino and Rangan (1995). Inter-firm relationships in the industry had become common by the mid-1980s in the United States and other industrialized countries soon joined this trend as deregulation advanced in the 1990s (Joshi et al., 1998, Trillas, 2002. Managers in the telecommunications industry should therefore consider the development of inter-firm relationships as their most important strategic activities, and a present matter of importance to them is evaluating inter-firm relationships. Managers engaged in developing inter-firm relationship strategies must decide whether to form inter-firm relationships, and which firms to target as potential partners. Such decisions must offer them the opportunity of improving the firm's competitive scope, increasing profitability, or gaining positive acceptance by stakeholders. Therefore, effective ways of evaluating inter-firm relationships are key tools for such managers and such tools would also be valuable to enable academic studies of these relationships.Although research has been conducted on inter-firm relationships in the telecommunications industry (e.g. Graack, 1996, Oh, 1996, Baroncelli, 1998, ChanOlmsted and Jamison, 2001, Curwen, 2001, Faulhaber, 2002, Jamison and ChanOlmsted, 2002, this has mainly focused on explaining specific relationships and discussion has mostly focused on rather qualitative standpoints. In this research, the authors have attempted to conduct quantitative evaluati...