In a long-term experiment conducted at Beltsville, Maryland by the USDA-ARS Sustainable Agricultural Systems Laboratory, five cropping systems (two conventional and three organic), differing in length and rotation, are compared with respect to yield and net returns, over four years. Conventional systems are two-year rotations of spring corn - fall wheat - summer soybean. The first of these is a no-till system with synthetic nutrient and weed management. The second utilizes synthetic nutrients, and tillage for weed management with synthetic rescue if necessary. The three organic systems are of two-year, three-year, and four-year rotation length, respectively. The first organic system is a corn-soy rotation. The second organic system is a corn-soy-wheat rotation, and the third is a corn-soy-wheat-hay rotation. All organic systems utilize legume cover crops and compost to supply nutrients, and cultural weed management. Enterprise budgets were constructed for each crop in each year, based on actual field activities that occurred in each rotation. Net returns by crop and by year were calculated for each rotation by subtracting variable costs from revenue. This economic evaluation is part of a larger effort to compare and predict the overall sustainability of these cropping systems, which includes agronomic, environmental, and economic components.