We appraise the monitoring activity of security analysis from the perspective of the manager–shareholder conflict. Using a data set of more than 7,000 company-year observations for manufacturing companies tracked by security analysts over the 1988–94 period, we found that security analysis acts as a monitor to reduce the agency costs associated with the separation of ownership and control. We also found, however, that security analysts are more effective in reducing managerial non-value-maximizing behavior for single-segment than for multisegment companies. In addition, the shareholder gains from the monitoring activity of security analysis are larger for single-segment than for multisegment companies.