Abstrak This research studying PEPERA (Penentuan Pendapat Rakyat) as the controversial event in resolving of the Dutch-Indo conflict in Irian Barat 1969. History method is the basic research method that usually used for studying the history event. The researcher divided the problem of this journal into three points 1) How is the situation of social and politic in West Irian (Irian Barat) before PEPERA in 1969?; 2) How is the process of PEPERA?; 3) How are the responses (pros-cons) of people of PEPERA? Dutch had established police school and Pamong Praja in West Irian which had purposed to plant ethonationalism in Papua and by developing educated new class who support Dutch colonialism. Dutch government afforded to reduce the new group who supported integration with Indonesia. Dutch government proclaimed the promise of Independence for West Irian by establishing Papua National Committee. The Dutch-Indo conflict ended in the New York treaty in 1969. One of the point of the treaty was West Irian was grated the freedom to choose independence or integrating herself into Indonesia. The result of referendum was West Irian choose to integrate with Indonesia. It became contravention when the process of PEPERA firstly announced by the Pro-Papua group after the area had been defeated by the Dutch. They claimed that the result of PEPERA was not legitimate because it was not taken by the conception of ‘one man one vote’ The contravention added with the fact when DMP or Dewan Musyawarah PEPERA who had represented Irian Barat for Indonesia had got the intimidation that made them to choose became the part of Indonesia. This group also claimed that the court who had presented by UN was illegitimate because was not adjoined to West Irian people needs. In another side the pro Indonesian group though that the result of PEPERA was legitimate based on New York treaty. The result of PEPERA resulted that West Irian was official became the part of Indonesia and legitimized by the President Decision and the formal court of United Nation (UN).