We examine empirically the long-run effects of reductions in minimum trading units (MTU) on stock prices in Japan from October 2001 to May 2008. When firms reduce their MTU, the number of individual shareholders tends to increase significantly for several years. We estimate buy-and-hold abnormal returns and find that positive stock returns are observed not only for the period between the announcement day and the actual date of MTU decreases, but also for a period of several years following MTU reductions. In addition, we measure stock price reactions to the release of public information before and after MTU reductions and find that stock prices react less to the release of positive information and more to the release of negative information after the MTU reductions. These findings, together with evidence of the change in the short and long positions of investors after the MTU reductions, indicate that individual investors face short-sales constraints.