The conventional assumption in the asset pricing literature is that the identity of a company's owners is largely irrelevant, but studies of companies with “blockholders”—shareholders with large positions in a particular company—provide grounds for questioning this assumption. Unlike the well‐diversified investors of modern portfolio theory, blockholders have strong incentives to monitor corporate performance and, when necessary, to exert control over ineffective managements and boards. The findings of many studies support the idea that blockholders have a positive effect on rates of return.The authors of this article report the findings of their recent investigation of whether blockholders might also have a positive effect on shareholder value by reducing the risk of the companies in which their holdings are concentrated. After distinguishing between companies with individual as opposed to corporate blockholders, and those with one share, one vote as opposed to those with dual‐class shares, the authors find that ownership of large positions by individuals—but not corporations—was associated with lower systematic risk (when using both Fama‐French multiple factor and CAPM models). At the same time, they find that the firm‐specific risk of such companies was higher, but “biased” toward positive outcomes—that is, smaller downsides with larger upsides. What's more, this upward shift in performance and risk‐profile was achieved at least partly through increases in productivity as reflected in higher profit margins, profitability, profit per employee, and operating leverage, and lower costs of goods sold, SGA, and cash holdings. By contrast, in the case of blockholders in companies with dual‐class share structures, all of these positive associations with blockholders were either significantly weaker, or reversed. That is, whereas the presence of individual blockholders appears to increase productivity and value under a one share, one vote governance regime, blockholders in companies with dual‐class structures were associated with higher systematic risk and reduced productivity and value.