This paper describes inter-firm partnerships in three major high-tech industries over the 1985-2005 period. We found that the architecture of the respective networks had evolved toward a ‘small world' in the early 1990s. We also found that the number of alliances collapsed in the late 1990s. This result roughly follows the number of patents granted in the respective industries and is correlated to an increase in market concentration, and to some extent to the rising number of mergers and acquisitions.