The EcoTrends Project is one of the first attempts to standardize, simplify, integrate, and visualize data from diverse terrestrial, aquatic, and marine ecosystems to promote understanding and synthesis by a broad audience. This chapter discusses key scientific results from this project, describes developing conceptual and operational frameworks for cross-site synthesis, and provides recommendations for future research. Key results are: mean air temperature has increased at 24 sites, and annual precipitation has increased at 9 sites with no obvious spatial distribution in either climate variable. Trends in atmospheric chemistry show clear patterns across the continent with reduced deposition of nitrate and sulfate in precipitation through time in the eastern U.S. compared with the West. Patterns in stream water chemistry across sites do not reflect broad-scale patterns in atmospheric chemistry; thus local conditions have strong influences on chemical inputs to and losses from streams. Human population density has increased at all sites, although at different rates. Biotic data are often idiosyncratic in that they reflect high spatial and temporal variability inherent in biological phenomenon.  It is proposed that cross-site synthesis studies should integrate three aspects of ecological research: depth (individual sites being studied in great detail), length (data being collected over long periods), and breadth (phenomena being studied across broad spatial extents).  The strongest recommendation for future research is to make data and associated metadata easily accessible to and usable by others.