The growth of the number of inter-firm strategic technology alliances during the 1980s has led to considerable attention to this phenomenon in recent years. In this paper an attempt is made to understand not only basic trends in the growth of inter-firm cooperation in sectors such as chemicals, aviation/defence, automotive and heavy electrical equipment, but also to reveal the role played by a large group of cooperating companies. The research is based on a large databank with information on thousands of alliances and their participating companies. Through statistical analysis it is possible to identify the major players within these sectors. The analysis enables us to recognize the major international networks of inter-firm alliances, the changes over time and different positions taken by world leading companies.