There are two main contributions of this dissertation. The first is to document the ownership concentration of publicly traded Brazilian companies in initial public offering (IPO) and in the subsequent years. The second is to show how the protection of minority shareholders rights influences the dynamics of ownership concentration in Brazil. The empirical literature on Finance identifies the existence of high degrees of ownership concentration in countries like Brazil, where the market provides weak protection for the rights of minority shareholders. The prevailing view is that this concentration reduces the risk of changes in control that would entail the loss of private benefits not internalized by the stock prices. In line with this scenario, this essay confirms that, on the dates of the IPOs that have taken place in Brazil from 2004 to 2011, the average participation of the largest shareholder is greater than 50 percent. Within five years of the date of the IPO, the average participation fell from 50 percent to 39 percent, an important drop although smaller than observed in US. A possible reason for this fall is the disciplinary function of the equity markets. The stock market would reduce the prices of the shares of companies that do not respect the rights of its minority shareholders, inducing such firms to delisting. The counterpart of this punishment would be a better valuation of the stocks of survivor companies, encouraging their controllers to diversify wealth by selling stocks, reducing the concentration. In fact, the data analyzed in this dissertation show that there is a positive correlation between ownership reduction post IPO and the issuance of American Depositary Receipts (ADR). The literature of corporate governance indicates that emerging-market companies submitted to the monitoring of the American capital market regulator - the Securities Exchange Commission (SEC) - compromise with practices of protection to the rights of minority shareholders. Thus, this positive correlation is consistent with the hypothesis associated with a disciplinary effect on the controlling shareholders. This dissertation identifies other factors correlated with the reduction of concentration after the IPO, and also concludes that this decrease in ownership concentration does not influence the long-term performance of stock returns.