Those making environmental decisions must not only characterize the present, they must also forecast the future. They must do so for at least two reasons. First, if a no-action alternative is pursued, they must consider whether current trends will be favorable or unfavorable in the future. Second, if an intervention is pursued instead,they must evaluate both its probable success given future trends and its impacts on the human and natural environment. Forecasting, by which I mean explicit processes for determining what is likely to happen in the future, can help address each of these areas. Certain characteristics affect the selection and use of forecasting methods. First, the concerns of environmental forecasting are often long term, which means that large changes are likely. Second, environmental trends sometimes interact with one another and lead to new concerns. And third. interventions can also lead to unintended changes. This chapter discusses forecasting methods that are relevant to environmental decision making, suggests when they are useful, describes evidence on the efficacy of each method, and provides references so readers can get details about the methods. A key consideration is whether or not the forecasting methods are designed to assess the outcomes of interventions. The chapter then examines issues related to presenting forecasts effectively. Finally, it describes an audit procedure for determining whether the most appropriate forecasting tools are being used.