The composition of acid-precipitated caseins from ruminant Mongolian domestic animals was analyzed and a comparative study between camel (Camelus bactrianus) and dromedary (Camelus dromedarius) was realized. Acid-precipitated whole caseins were analyzed for amino acid composition, separated by anion exchange chromatography and identified by alkaline urea-PAGE. Elution profiles and electrophoretic mobilities of the main components of yak and khainak caseins were nearly identical to their cow counterparts. However, the main part of α S 1 -casein of yak was eluted in lower molarity in NaCl. Characterization by PAGE, amino acid composition and N-terminal sequence of individual caseins from camel (Camelus bactrianus) indicated that milk of this ruminant contains dominantly α S 1 -, α S 2 -, and β-casein and small amounts of κ-casein as is the case for the milk of dromedary (Camelus dromedarius).La composition en acides amines des caseines totales de deux ruminants de Mongolie (yak, khainak) a ete determinee. Les differentes caseines ont ete separees par chromatographie sur echangeur d'ions et analysees par electrophorese en milieu uree et a pH alcalin. Les caseines des deux especes etudiees ont un comportement voisin, proche de celui des caseines de vache. La seule difference notable reside dans le fait que chez le yak, la caseine α S 1 est eluee a une molarite inferieure a celle utilisee lors de la separation des caseines de vache et de khainak. Une etude comparative a ete realisee entre le chameau (Camelus bactrianus) et le dromadaire (Camelus dromedarius). Ces deux especes renferment principalement les caseines α S 1 , α S 2 et β, dont la sequence N-terminale a ete determinee. La caseine κ n'est que faiblement representee.