The Bureau of Mines has investigated the resource potential of 201 phosphate mines and deposits in 28 market economy countries and 17 mines and deposits in the U.S.S.R. and China. The 201 mines and deposits contain an estimated 34.2 billion mt of recoverable phosphate rock (at the demonstrated resource level), with Morocco and western sahara accounting for 61 pct (21 billion mt) and with the United States accounting for 19 pct (6.4 billion mt). The 17 mines and deposits evaluated in the U.S.S.R. and China contain approximately 1.5 billion mt of potentially recoverable phosphate rock. Potential annual capacity from low-cost, high-grade producing mines in the United States is estimated to decline significantly during the latter half of the next decade, and the U.S. phosphate fertilizer industry will have to obtain phosphate rock by developing new, higher cost, lower grade mines or import phosphate rock to satisfy anticipated demand in the next century. Of the world's new production capacity that is likely to be developed over the next decade, slightly over one-third could be produced at an estimated 1981 cost of $40/mt or less, and about two-thirds would cost in the $40 to $50 per mt range (including a 15-pct rate of return). In comparison, most of the competing phosphate rock from producing mines in Morocco could be produced for less than $40/mt.