Mergers and acquisitions are frequent phenomena in everyday business activities (Holtström,2008). For a merger or an acquisition, expected synergy is of fundamental importance. Thesynergy-concept emerged in the business strategy literature in the 1960s and has since then gainedimmense influence as a strategic tool for CEOs and company boards. In both theory and practice,synergy describes value creation of some kind (Pernod Ricard, 2008; Arya, 2002; Rozemeijer,2000; Tapper, 1999; Larsson & Finkelstein, 1999; SvD, 1998; Olsson, 1997; Chandler, 1992;Trautwein, 1990; Porter, 1987; Rydén, 1971; Ansoff, 1965). Having a business network structureperspective as point of departure, we assume that mergers and acquisitions will involve andintegrate not only the acquirer or the acquired company but also connected companies such ascustomers and suppliers (Holtström, 2008; 2003; Öberg, 2008; 2004; Dahlin, 2007; Öberg &Holtström, 2006; Anderson, Havila & Salmi, 2000; Havila & Salmi, 2000; Bengtsson, 1994).Synergy as concept (cf. Goold & Campbell, 1998; Itami, 1987; Lubatkin, 1983; Ansoff, 1965) isin this paper further developed and extended to comprise also synergy in the integratingcompanies’ business network. The paper aims to develop a framework to describe synergy inbusiness relationships with customers and suppliers. To achieve this we first need to analyse howsynergy is realised within a company. The analysis is based on a case study of mergers andacquisitions among industrial companies having business in Sweden.Our findings indicate that within a company synergy is the result of the interplay between creationof value, alignment between strategic prioritisations and functional performance. Thus theintegrating companies are at the core. The application of synergy in the M&A-companies businessnetwork is to include also their business relationships with other actors. So in a second analysis,we show that synergy in business relationships can be seen as the result of how companies a) adaptto changes in the business network, b) how the changes affects interdependency among actors, c)to what extent there is a co-ordination of activities between actors, but most importantly d) howthis is carried out over time.The resulting framework on connected synergy, combines the perspectives on synergy describedabove with also the development over time. Within the M&A-companies, two forms of synergyappears; (i) planned in the early phases of integration and, (ii) emerging over time. In the M&Acompanies’business relationship synergy can appear as (iii) something planned by the integratingcompanies to purposely influence other actors and, (iv) developing when different actors adapt tothese changes over time.