This chapter addresses the question of how research on environmental assessment, cognition, and action can be utilized in the professional arenas of public policy, urban planning, and architectural design. Initially a discussion on three papers (Chapters 12, 13, and 14), the chapter attempts to extrapolate policy and design implications for the built environment from current knowledge on life-span developmental issues as represented by these three chapters. Suggestions of other research questions, issues, and strategies that might better inform policy and design are then discussed. In conclusion, the chapter briefly explores six general issues about the interaction of environmental cognition and research utilization. The contributions to this volume by Giovanna Axia, Erminielda Mainardi Peron, and Maria Rosa Baroni, by Lynn Liben, and by Roger Hart and Michael Conn have dealt heavily with child development and very little with aging or life-span development. Little evidence is presented from the gerontological and geriatric literatures, and less from the life-span literature. Liben presents a clear conceptualization of lifespan developmental approaches to environmental cognition, but to date there have been few studies and thus no data specifically on life-span developmental changes in environmental cognition. My chapter, therefore, will be weighted most heavily on the earlier phases of human development though, where feasible, it will comment on implications for the environment of elderly adults and on the environmental context of life-span developmental changes. Despite their titles and intentions, the three chapters focus most heavily on environmental cognition and much less on assessment and action. For example, after discussing the wide variety of possible definitions of assessment, including appraisal, evaluation, preferences, and attachment. Axia et al. focus most heavily on the cognitive aspects of schemata, representation, and organization of knowledge. Similarly, Hart and Conn valiantly take on the challenge of reporting on children's decision making and environmental behavior, but their empirical examples are also limited to cognitive and metacognitive issues. My chapter will thus also focus on environmental knowing. There are many interesting points of a theoretical and conceptual nature to raise about environmental assessment, cognition, and action from these three chapters, but this task is left to the other commentary chapter by Christopher Spencer.