North American methods of uranium ore processing include leaching with either sulphuric acid or a soda ash-sodium bicarbonate mixture. From the acid leach solutions, either solvent extraction or ion exchange extracts high grade uranium, which is then precipitated with ammonia or magnesia. Finer grinding, higher temperatures, and sometimes pressure are required with the alkaline leach. Uranium mills can now be built with confidence in design and performance. The average capital cost for acid leach mills for 500 to 5500 tons of ore per day varies from $7550 to $3350 per ton daily, respectively; alkaline leach mills cost 10% more. Direct milling costs range from $0.88 (New Mexico) to $1.53 (Elliot Lake, Canada) per pound of U3O8 recovered and are decreasing in many of the operations. Ore grade has little effect cm recovery yield or on cost per tan milled but a marked effect on cost per pound of U3O8 recovered. Although demand is for yellow cake, the integration of mining, milling, and refining operations could eliminate the yellow cake precipitation step and save 7 to 11¢/lb U. Direct production of UF4 is feasible, but ammonium diuranate is a good versatile product, and there is little economic advantage to feeding refineries with high purity concentrates.