a 2008). On the other, technological discontinuities bring about new opportunities and, thus, new entrants to the market. Maturity and discontinuities both in turn increase the number of mergers and acquisitions (M&A) on the vertical software market, and over 50 of M&A have occurred in the OSS market within the last seven years. M&A activity offers an interesting topic for analysis as it gives indications on the vendors' business strategies and on the future of the vertical software market. In the following the aim is at finding out the impact of M&A activities on the structure of the telecom software market. The focus is on the horizontalization of the market that can increase as result of natural evolution of software market or through M&A activities. Horizontalization here refers to the development in soft- ware systems where is becomes possible to provide the same software system (1) for two or more customers within the same industry, (2) across technologies and (3) across industries. Horizontalization is also defined as development where a soft- ware vendor (4) expands their offering to new segments within a vertical software market or (5) enters new vertical software market. The natural evolution enabling horizontalization occurs mainly through standar- dization, which reduces the barriers of entry to the software market or its segment. Standardization of business processes in a vertical industry enables providing software for many customers and reduces importance of special knowledge on vertical processes. Standard interfaces in turn enable modular systems and software product architectures and pre-integrated software products. Mergers and acquisition conversely are considered as a means to capture resources or knowledge that software vendors cannot develop internally and are unable to acquire as discrete companies. A number of contributions, in particular in the strategic management literature, links up to the motivations of M&A activities. For achieving its aim, this section analyzes the M&A activity of 