The electronic industry is often taken by scholars as an example of a sector driven by high competition between few large companies and endless technological innovation, hence embodying the classical theory where the free market leads companies to innovate. On the other hand, some business historians have also emphasized that, since the beginning of the 20th century, in particular since the 1920s, most of these companies were engaged in various international cartel agreements for some goods such as incandescent lamps. Literature in business and economic history on this industry shows a clear-cut divide between the interwar years and the postwar era. In this paper, however, we argue that technical and commercial cooperation between large electronic companies was not limited to the prewar area and that it continued in various forms, despite the spread of anti-trust policies after 1945. In this case study we explore the global X-ray equipment industry from its beginnings around 1900 to the advent of the CT scanner in the early 1970s. The X-ray technology can be seen as the beginning of a lucrative medical equipment industry. The paper focuses on Siemens and Philips, the two largest manufacturers of radiological equipment in the world in the Twentieth Century. It addresses the following questions: Why and how did electronic firms with in-house R&D facilities and global distribution networks decide to cooperate? What were the limits of this cooperation, and at what point did these firms decide to compete? How did these relations change over time?