This Bureau of Mines study assesses the economic significance of the Florida phosphate industry to selected counties in Florida, the state of Florida, and the nation; it also includes a brief survey of the industry's international impact. Based on forecasts of Florida phosphate production in 1981, and using constant 1977 dollars, estimates are given for 1981 for regional and national output, the value of this output, income, and employment created by the phosphate industry in Florida. Federal, state, and county tax revenues generated by the state's phosphate industry are also estimated for 1981. The concentrated impact of the phosphate industry on certain areas of Florida and on the state's regional industries is examined using economic base analysis complemented by an industrial complex approach. The industry's impact at the state and national levels is examined through input-output analysis. In addition, an attempt to forecast for 1990 the effects of constraints on phosphate rock mining as a result of economic conditions and other factors is included as an appendix to the report. Also discussed is the phosphate industry's importance to the U.S. balance of trade; U.S. agricultural production, including forward linkages; the U.S. sulfur industry; and the phosphate industry's importance to the production of fluorine and uranium byproducts from fertilizer manufacturing.