Benefit-cost analysis is a method to measure the economic desirability of an activity, project or policy to the community as a whole. Issues in the application of the method to the management of weeds in natural environments are identified from a review of past applications. Opportunities are also identified from the review and the requirements for effective benefit-cost analysis. The valuation of benefits, and the treatment of risks, appears to be major areas for development - despite the advances in these areas over recent years. There is a need for production functions to relate weed spread to the outputs of natural environments, and the relevance of partial analyses appears to warrant examination.