Nuclear waste cleanup is a challenging and complex problem that requires both scientific analysis and dialogue among a variety of stakeholders. This article describes an effort to develop an online information system that supports this analytic-deliberative dialogue by integrating cleanup information for the Hanford Site, and making it more “transparent.” A framework for understanding and evaluating transparency guided system development. Working directly with stakeholders, we identified information needs and developed new ways to organize and present the information so that it would be more transparent to interested parties, with the ultimate aim of fostering greater participation in decision dialogues and processes. The complexity of the information needed for dialogue suggested that several types of communication devices (“information structures”) were warranted. Five information structures were developed for the pilot Decision Mapping System (http://nalu.geog.washington.edu/dms). Decision maps hyperlinked decision information to maps of Hanford. Background Information provided context in a narrative format. Decision Paths organized decision process information on a timeline and provided direct hyperlinks to online documentation. The Geographic Library hyperlinked decision documents to maps. Finally, a Discussion Forum allowed users to make comments and view remarks from others. Early lessons from this work suggest that transparency is integral to long-term management, a participatory design process contributed greatly to its perceived success, and better data integration to support decision making is needed. This work has broad implications for risk communicators and risk managers because it speaks to the design of information systems to support “analytic-deliberative” decision processes (i.e., those that rely upon both risk science and public dialogue).