The objectives of this research are to determine the phylogenetic relationships among populations of Macaca fascicularis in Malaysia. This research involved 14 individuals of Macaca with locus Cytochrome C Oxidase subunit I (COI). DNA was extracted from blood, tissue and liver. Nine individuals which are species M. fascicularis, M. nemestrina, Trachypi thecus cristatus and Trachypithecus obscurus were used to generate phylogenetic relationships among populations of M. fascicularis. COI region sequences of mtDNA have been obtained in size of 700 bp from PCR process. Then, by using the genetic softwares which are Bioedit, MEGA, ClustalW, PAUP and MrBayes, the samples...