Abstract: In a process according to the present invention uranium is extracted into solution from its ore by leaching with an aqueous solution containing peroxomonosulphuric acid, the peroxoacid oxidizing the uranium through to its hexavalent state. Preferably the leaching is carried out at a temperature in the range of 50.degree. to 100.degree. C. The leach liquor can initially contain additional amounts of sulphuric acid or merely that present by virtue of the method of making the peroxomonosulphuric acid. In a preferred method of operation, the peroxoacid is introduced progressively into the leach liquor during the course of the leaching so as to maintain an electrochemical potential in the range of 450 to 650 mV.By use of the process, uranium is cleanly extracted into solution.