© 2008 the American Finance Association. We relate the property rights theory of the firm to empirical regularities in the market for mergers and acquisitions. We first show that high market-to-book acquirers typically do not purchase low market-to-book targets. Instead, mergers pair together firms with similar ratios. We then build a continuous-time model of investment and merger activity combining search, scarcity, and asset complementarity to explain this like buys like result. We test the model by relating like-buys-like to search frictions. Search frictions and assortative matching vary inversely, supporting the model over standard explanations.