Recent clinical studies have demonstrated that feeding with asses milk is a safe and valid treatment for infants affected by protein intolerance to dairy cows milk (Businco et al., 2000; Iacono et al., 1992). In fact, the composition of asses milk is similar to humans milk, especially concerning the lipid and protein fraction contents (Fantuz et al., 2001; Salimei et al., 2004). Furthermore, the protein fraction in asses milk is characterized by low casein and β-lactoglobulin content, probably responsible for the hypoallergenic characteristics of this milk, and by a quite high lysozime content (Fantuz et al., 2001; Salimei et al., 2004). In any case, there is not much information regarding the caseinic fractions of asses milk in the literature. Therefore, in the present study αS1and β-caseins were purified from asses milk by gel filtration chromatography followed by anion exchange chromatography on HPLC. The obtained caseins were characterized by SDS-PAGE and, after blotting on a PVDF membrane, were identified by N-terminal sequencing.