Abstract: The present invention relates to a process for treating residues from a primary leaching of ferriferous zinc ores by sulphuric acid, with a view to recover a leadbearing by-product, such process comprising a secondary leaching of said residues, by sulphuric acid, within several countercurrent stages, at a temperature comprised between 85.degree. and 100.degree. C., the solid residues of the successive stages being circulated from the first to the last stage, the residue of this last stage being the said lead bearing by-product, whereas the various solutions separated from the second to the last stage are each recycled within the leaching operation of the respectively foregoing stage, and the dual zinc and iron sulphates solution, as separated from the first stage, being the principal product of the treatment.