This paper aims is to analyze the behavior of stock prices of publicly traded Brazilian companies listed on the BM & FBovespa the day after the announcements of mergers and acquisitions (M & As) to measure the semi-strong form of the Market Efficiency Hypothesis of the Brazilian market. This study considered an event in which the daily abnormal returns were calculated using the model of market-adjusted return. The sample consisted of 61 preferred and 27 common shares of Brazilian companies participating in processes of M & A between January 1996 and December 2004. The results indicated that 1. The announcement of an M & A event contains information relevant to the pricing of shares in the market; 2. The possible use of inside information; 3. The Brazilian market is represented by the semi-strong form of the Market Efficiency Hypothesis, both for preferred shares and for the ordinary shares, with regard to the speed of adjustment to announcement; 4. The market reacted differently to common and preferred shares, decreasing for the former and increasing for the latter.
Market efficiency; Mergers and acquisitions; Event study; Insider trading
