Abstract: The invention relates to a process for the treatment of an uraniferous ore containing sulfur in the form of sulfates or sulfides with one or more alkaline solutions containing sodium carbonate in the presence of an oxidant, for extracting uranium in the form of soluble uranium salt in said solution.It comprises subjecting the ore, in a first step, to the action of a dilute pre-leach solution of sodium carbonate, whose concentration does not substantially exceed, or by very little, that which is required for the solubilization of the major part of the sulfur initially contained in the ore to convert it to sulfate in the presence of the oxidant and, in a second step, to the action of a leach solution, more concentrated in sodium carbonate, enabling the extraction and solubilization in the medium of the major part of the uranium still contained in the ore, not extracted in the pre-leach medium of the first step.