He was a member of the Communist Party of the Philippines' Central Committee, along with Jose Maria Sison and Luis Jalandoni during the Marcos dictatorship.
On his release, Agcaoili founded the Samahan ng mga Ex-Detainee Laban sa Detensyon at Aresto (SELDA), a prisoners' rights organization.
Agcaoili continued to serve in the peace panel, becoming co-chair of the GRP-NDFP Joint Monitoring Committee in 2004, and eventually succeeding Jalandoni as chief negotiator in 2017.
[1] Agcaoili was born to an "upper class family" and "could have easily attained an endless series of high positions in the ruling system.
[4] Norberto Basilio, who would eventually become the Philippine ambassador to Greece and Bangladesh introduced Agcaoili to Jose Maria Sison and Julie de Lima.
Agcaoili joined a Marxist study organized by Sison,[2] which took place in the private residence of ambassador Emilio Bejasa.
Basilio, Bejasa Jr., and Agcaoili would continue to maintain close contact during the Martial Law years as members of the Communist Party of the Philippines.
He organized studies, produced publications, and entered negotiations with other local and foreign parties, and eventually contributed to the reorganization brought about by the First Great Rectification Movement.
State agents gave him morphine injections to induce addiction, the idea being that the withdrawal would be so severe as to force him to give up information.
He formed the Samahan ng mga Ex-Detainee Laban sa Detensyon at Aresto (SELDA), a prisoners' rights group.
[1] Agcaoili was also involved in the Preparatory Committee which established the Partido ng Bayan (PnB, precursor to Bagong Alyansang Makabayan) on August 30, 1986.
Agcaoili took over as Chairman when labor leader Rolando Olalia and his driver Leonor Alay-ay were kidnapped and murdered by elements of the Armed Forces of the Philippines as part of the "God Save the Queen" plot, in time for the 1987 senatorial elections.
[1] In 1988, Agcaoili was targeted for arrest and decides to go on voluntary exile in Europe, taking a job with the Spanish non-government organization Instituto de Estudios Políticos para América Latina y Africa (IEPALA).
[7] Agcaoili and Ocampo collated the names and experiences of some 10,000 victims of human rights abuses during the Marcos dictatorship and brought the case to court in Hawaii.
[8] Agcaoili joined exploratory talks between the GRP and the NDFP in 1989 when President Aquino sent Jose Yap to the Netherlands to negotiate.
In 2016, he replaced Luis Jalandoni as chairperson of the NDFP Negotiating Panel,[10] in time for the resumption of peace talks under Rodrigo Duterte.
"[15] Contemporaries remembered Agcaoili as taking on the smallest details, such as making travel arrangements and picking up consultants at the airports, despite his high-ranking position.
"[16] Former Quezon City mayor Herbert Bautista, who was also a part of the GRP Panel, called Agcaoili "funny, but firm and serious on the negotiating table.
"[13] The Communist Party of Canada (Marxist-Leninist) published a short statement in its publication, calling Agcaoili's death a "great loss to the CPP, the NDFP and the entire Filipino people.