The aim of the present work was the recovery of nickel and copper from metal finishing hydroxide sludges by ammoniacal leaching. Actually the study was split into two main parts. First, the recovery of the metals in the presence of ammonia was subjected to theoretical approaches followed by numerical and computer calculations to determine optimal leaching conditions (pH and total concentration). In this part the solubility diagrams were plotted versus two parameters: pH and [NH3]T. second, the study was carried out experimentally. The work was performed on pure metals hydroxides and then on electroplating sludges. The solubility variation versus pH at various ammonia concentrations and versus ammonia concentration at various pH values was conducted keeping the free ammonia concentration on the diagram to show the stability regions of soluble metal species. Optimal ammonia concentration for leaching [NH3]total at pH58 to 11 was found to be less than 6 mol L21, and a recovery experimental flowsheet was proposed.