Statewide planning requires a variety of transportation system, land use, passenger, freight, demographic, economic, and environmental data from many different federal, state, regional, and local sources. Establishing effective partnerships for sharing data can optimize available resources and enhance the quality of data brought to the decision-making process. Evidence also shows that sharing data early in the decision-making process increases stakeholder support and decreases process timeframes. Connecting disparate data sets is often complicated by cultural and institutional factors, as well as how data are defined, collected, derived, stored, and managed. New intelligent transportation systems (ITS) and geographic information system (GIS) technologies for collecting data are raising additional challenges relative to data translation, data archiving, and the integration of spatial data with differing accuracies. To address some of the benefits and challenges facing the development of transportation data partnerships, a Peer Exchange was held on May 21, 2003. Participants shared recent endeavors in data sharing for statewide transportation planning. From the discussions, a synthesis of effective strategies, methods, and tools was identified for addressing factors that influence the sharing of spatial and other data between and within federal, state, and local governments.