Do health and health policy professionals (HHPPs) participate in the formation of agency health regulations? Passage of the Patient Protection and Affordable Care Act (ACA) of 2010 has necessitated the writing of many health-related national and state regulations. This article examines the participation patterns of HHPPs during rulemaking to gain insights that may be transferable to future health-related administrative decision making. The author suggests that the mix of public participants active during rulemaking has implications for health policy outputs. This proposition is tested using data drawn from 39 state health regulations and survey data from more than 380 participants and 23 interviews with agency officials. The author finds that HHPPs participate across the majority of the sample regulations, and when their activity across a rule increases, so does participant satisfaction with regulatory outcomes. More broadly, the results suggest a desire for even greater participation by HHPPs in future health-related rulemaking.