Andreas Hammer, Alexander Knauer, Magnus Pflücke, Bernhard Schwetzler

• We study add-on acquisitions of portfolio _x000C_firms based on a world-wide data sample covering 9,548 buyouts between 1997 and 2012. We _x000C_find that add-ons have become increasingly relevant, but activity is concentrated among a few PE sponsors. Further, our results suggest that synergies are important when pursuing add-on acquisitions. We show that portfolio _x000C_firms initiate acquisitions early to realize synergies until the exit. Lastly we identify determinants that increase the likelihood of add-ons for a particular buyout. Our _x000C_findings help academia and practice to understand inorganic growth in buyouts, which is important given the aging of the industry.