The importance of the benefication process need not be over emphasized. The presence of high amounts of low- and intermediate-grade phosphate ore and the need for high-grade ore for industry necessitates the availability of economic and efficient upgrading techniques. The fluidized bed technique is the most suitable for thermally upgrading ores containing high percentages of organic matter, carbonates and moisture. In this investigation, studies were carried out on the process of thermal upgrading of Mazidagi (Turkey) phosphate rock in a fluidized bed. The studies involve the effect of the important variables such as process temperature, air flow rate, particle size and attrition of phosphate particles. The calcined product was water-leached. The P2O5 content was determined by a spectrometric method. It was found that the increase in process temperature favorably affected the percent upgrading of the ore. The fluidizing air flow rate slightly affects the upgrading process. The use of high air flow rates increases the extent of attrition of phosphate particles. The particle size of the phosphate affected the upgrading efficiency of calcination. Fine sizes were favorable. Washing of the calcined ore was inefficient with the fine sizes and at low temperatures.