The Northern Forest is among the largest areas of relatively intact and undeveloped forest in the eastern United States. Increasing changes in landownership, wood extraction, nutrient cycling, air pollution, global change and other human-caused impacts raise concern about the long-term ecological and economic health of the forest. The division of the Northern Forest among several distinct groups of landowners and rapid changes in global economics make the forest potentially vulnerable to large-scale fragmentation and development. We examined and characterized the current status of and potential threats to various aspects of the Northern Forest at the levels of ecosystems, populations, and forest nutrients, including land-use patterns, extent of forested area, species diversity, biological threats such as introduced species, pests and pathogens, and air and water quality. Our findings reveal that the total area of the Northern Forest and the sum total of tree growth minus tree removals is approximately stable, although there are variations within the region. Tree species diversity in recent decades is approximately stable. A number of viable woodland bird species show significant decreases both in the long-term and short-term while others are increasing in abundance. The water quality of most lakes, streams, and rivers, while generally improving, is still hampered by high levels of mercury, PCBs, and other contaminants in fish tissue. Land development and habitat fragmentation have remained a minor threat to the health of the Northern Forest in comparison to more highly disturbed forests (e.g., tropical forests). These trends suggest that the Northern Forest remains in fairly stable condition, but the continuation of this pattern will depend largely on whether or not trends in land purchases persist and if development-and resulting fragmentation-of the Northern Forest becomes economically attractive.