AbstractI study the effect of patent-infringement claims by patent trolls on acquisitions of small firms. Exploiting staggered adoption of state anti-patent troll laws, I find that the laws have two effects. First, the number of acquisitions of small firms declines after these laws are adopted. Second, the anti-troll laws increase the acquisition price for acquirers. The market reflects the increased cost of acquisition as measured by lower acquisition announcement returns. Large firms increase R&D after the adoption of state laws, replacing external innovation. Using a sample of acquisitions that are plausibly unaffected by the laws, I disentangle alternative explanations.