Casein glycomacropeptide (CGMP) is one of the whey protein which constitutes 12-20% of whey proteins approximately. It has various functional and biological activities. Such as growth-promoting effects on bifidobacteria, suppression of gastric secretion and the inhibition of viral or bacterial adhesion to intestinal epithel cells, inactivation toxins of Escherichia coli and Vibrio cholerae, inhibition adhesion of cariogenic bacteria with use in toothpastes. It also has good foaming emulsifying agent properties. The objective of this thesis was to develop a new functional food ingredient suitable for use by individuals with Phenylketonuria (PKU) that causes protein malnutrition. In line with this objective, CGMP was used as a protein source. It was isolated from caprine whey by ultrafiltration process. This process was applied with different parameters to obtain CGMP with high purity and yield. Protein fractions and Phenylalanine and tyrosine contents of CGMP isolates were determined by RP-HPLC. Some compositional analysis was carried.