Cropping systems are changing rapidly in the upper Midwest. Growers are increasingly adopting herbicide-resistant crop cultivars, particularly transgenic crops with resistance to glyphosate. Grower interest in glyphosate-resistant corn and soybean has rapidly and dramatically changed weed management practices. The potential exists on many acres where glyphosate is the primary, if not only, herbicide used for weed management in both cornsoybean rotation and in continuous-corn cropping systems Although growers are implementing these new technologies, many questions remain about the long-term impact of glyphosateresistant cropping systems on weed management. Limited research information has been available to growers about the potential for new weed problems, weed resistance to glyphosate, or the integration of glyphosate use with other cultural, mechanical, and chemical practices. Therefore, research was initiated in 1998 and conducted through 2001 at the University of Wisconsin Arlington Agricultural Research Station to determine the long-term weed management and agronomic risks in glyphosate-resistant corn and soybean cropping systems as influenced by primary tillage, crop rotation, and intensity of glyphosate use. Specific objectives were to determine changes over time in the number and type of weed species, weed plant density and biomass, soil seed bank density, and crop yield. Tillage treatments included moldboard plow, chisel plow, and no-tillage systems. Cropping system treatments included continuous corn and corn-soybean rotation. Weed management treatments included glyphosate only, glyphosate use integrated with other chemical and mechanical practices, and conventional herbicide programs. Among weed management treatments, glyphosate applied sequentially or glyphosate plus inter-row cultivation were among the most consistent and effective treatments in continuous corn. Results for these particular treatments since 1998 indicate that weed population densities have decreased over time. In corn-soybean rotation, most treatments that included glyphosate were effective for weed management, particularly in moldboard plow and chisel plow systems. Common lambsquarters, giant foxtail, and velvetleaf were the dominant weed species in most glyphosate-based treatments in each cropping system, but these occurred at low to very low densities. In contrast, giant ragweed and/or shattercane populations increased over time to become the dominant weed species and serious weed management problems in treatments that included broad-spectrum preemergence soilresidual herbicides. Results suggest that the weed management and agronomic risks associated with glyphosate use in glyphosate-resistant corn and soybean were no greater than those associated with conventional preemergence soil-residual herbicide programs.