This study was carried out in order to establish a relationship between Protein/fat ratio, free amino acids, and casein fractions of cow, buffaloe and goat milk. The amino acid contents of the examined milks were also detected quantitatively and qualitatively. Fat and protein contents generally increased in milk during the period extended from may until the end of laction period. Aspartic acid and glutamic acid were found to decrease in goat milk, which explains the increase of formalin coefficient. The goat milk characterized with an increase in phenylalanine, lysine and histidine. Casein of buffalo's milk was of higher content of isoleucine, and completely free from lysine, proline, glutamic and serine. Casein of goat and cow relatively contained the same concentration of cysteine, which is not found in buffaloe milk.