Rulemaking is one of the U.S. government\u27s most important policymaking methods. Although broad transparency and participation rights are part of its legal structure, significant barriers prevent effective engagement by many groups of interested citizens. RegulationRoom, an experimental open-government partnership between academic researchers and government agencies, is a socio-technical participation system that uses multiple methods to alert and effectively engage new voices in rulemaking. Initial results give cause for optimism but also caution that successful use of new technologies to increase participation in complex government policy decisions is more difficult and resource-intensive than many proponents expect