This paper examines the valuation consequences of external blockholdings. The stock market responses to announcement of block formations are positive, on average. Potential sources of gains to blockholders are identified, and the stock market responses are related cross-sectionally to firm-specific variables proxying for these sources and to blockholder-specific characteristics. The announcement period abnormal returns are explained by the potential for wealth transfer from bondholders, block size, and the identity of the blockholder. Changes in operating and performance variables following block formations provide weak evidence of hands-on monitoring by blockholders on an ongoing basis, suggesting that the observed value increases arise from expectations of future takeover gains and/or from limits on future opportunistic managerial behavior.
