Air quality planning practice in Central California is confusing, convoluted, and controversial.  It is also insufficiently successful despite years of planning and millions of dollars invested to improve scientific understanding and to implement emissions controls.  This study examines the use of science and the management of uncertainties to attain standards for ground-level ozone in San Francisco and the San Joaquin Valley.  Perspectives are gathered and analyzed through interviews with planners and modeling technicians at air quality management agencies, elite decision-makers at the California Air Resources Board, and representatives from the regulated and environmental communities.  The results provide insights about the potential for using new information and understanding to achieve air quality goals.  Practices to facilitate incorporation of scientific information are suggested based on interview findings, as well as suggestions from the literatures of the policy sciences, decision sciences, consensus-based planning, and modeling theory.