Technical Abstract: It has been commonly accepted that crop rotations reduce risk compared to monoculture systems. Quantifying this phenomenon requires that effects on risk from yield stability (positive or negative) arising from rotating crops be separated from other risk elements. Grain yield results from 14-years of a long-term cropping system study for maize and soybean grown in both rotation and in monoculture were used to isolate and estimate the impact of crop rotation on risk. Risk was defined as the failure to meet an annual per ha net return target. A maize-soybean rotation had significantly less risk than monoculture practices. Diversification was found to contribute to part of this reduction while higher yields and reduced cost contributed the remainder. This reduction in risk occurred even though grain yields in the maize-soybean rotation were less stable than yields in monoculture systems.