Protein hydrolysates were obtained by acid hydrolysis from animal or human residues, such as poultry feathers, ox blood and human hair. After neutralization and discolouration with active charcoal, the hydrolysates were treated by successive electrodialysis (ED) in order to extract amino acids into several fractions. The current density and pH were optimized for each ED operation performed with preindustrial pilot scale equipment. The first step was the demineralization of amino acid mixtures using an ED stack with two compartments. The salt removal was achieved with extraction degrees higher than 90% and current efficiencies of about 80%. In the most favourable case, the amino acid losses did not exceed 10%. The second step was the extraction of the charged amino acids using an ED stack with four compartments. Three fractions were obtained, corresponding to the acidic, basic and neutral amino acids. The extraction degrees varied from 80% to 100%. In the third step, the fractionation of basic amino acids on the one hand, and neutral amino acids on the other hand, was carried out with enrichment degrees varying from 50% to 80%.