In discussing the research needs in the area of land use and transportation, this paper focuses primarily on the topic of the linkage between land use and travel behavior. While a great deal has been learned in recent years about the ways in which land use and transportation interact, significant gaps remain in our ability to explain or to predict the outcome of specific land use policies and transportation-investment actions. Presented in this paper are some of the emerging areas where considerable effort is required to help provide practitioners with analytical tools and approaches to addressing the types of questions that are now surfacing. Some of these areas of inquiry have always been of great interest to planners, decision makers, and even the general public, but were not accessible. In some cases they are now becoming available through vast improvements in data and computing methods. The areas discussed are activity center design, residential location choice, "self-selection" or community preference, the Puget Sound Transportation Panel, conveyance and visualization, and equity considerations.