This study documents state implementation of mechanisms designed to promote public participation in agency rulemaking. Many scholars have questioned the effectiveness of such mechanisms, arguing that they fail to encourage greater participation or that increased participation does not affect the substance of administrative rules. Using data from a unique survey of state administrators, the author employs multivariate analyses to assess the relationship between these measures and the perceived influence of external actors. The results suggest that critics may understate the importance of public notification and access procedures. These devices are associated with increases in the impact that a wide variety of actors are perceived to have on the content of agency rules.