This dissertation analyzes the role of institutional investors in corporate governance. The first essay studies the effect of potential proxy contests on corporate policies. I find that when the likelihood of a proxy contest increases, companies exhibit increases in leverage, dividends, and CEO turnover. In addition, companies decrease R&D, capital expenditures, stock repurchases, and executive compensation. Following these changes, there is an improvement in profitability. The second essay investigates the optimal contract with an informed money manager. Motivated by simple structure of portfolio managers' compensation and complex risk structure of returns, I show that it may be optimal for the principal to stay unaware about the true risk structure of returns. The third essay analyzes the biases related to self-reporting in the hedge funds databases by matching the quarterly equity holdings of a complete list of 13F-filing hedge fund companies to the union of five major commercial databases of self-reporting hedge funds between 1980 and 2008.