The Leafy Spurge Biological Control program was designed to use insects and plant diseases from the plant's original European habitat to control infestations in the United States. The widespread adoption of biological agents to combat leafy spurge and the initial success in reclaiming previously infested land has prompted an evaluation of the potential future economic benefits of the biological control of leafy spurge in the Upper Midwest. Based on expert opinion and historical data, leafy spurge in Montana, North Dakota, South Dakota, and Wyoming was projected to infest 1.85 million acres, of which, 65 percent was estimated to controlled with biological agents by 2025. Based on a survey of county weed board personnel, North Dakota and Wyoming are further advanced in the use of biological control than Montana and South Dakota. Recovery of rangeland outputs resulting from the biological control of leafy spurge was estimated to create $52.7 million in direct and secondary economic impacts. Biological control of leafy spurge on wildland was estimated to generate $5.6 million annually. By 2025, total economic impacts of the Leafy Spurge Biological Control Program were estimated at $58.4 million (1997 dollars) annually in the four-state region. An additional 876 full-time equivalent secondary jobs would be created as result of the program. Although the economic estimates generated are based on expert opinion and remain sensitive to assumptions regarding the future efficacy of the biological control of leafy spurge, initial evidence suggests the program will be an economic success regardless of the eventual level of control. The assessment of the economic value of the biological control of leafy spurge would benefit from incorporation of additional information as the overall understanding of the biological control process grows.