At least 11 Latin American heads of state, possibly including Cuba's Fidel Castro, will watch President Alvaro Arzu and four guerrilla commanders sign the so-called Agreement for a Firm and Lasting Peace in the National Palace in Guatemala City.
Although the guerrillas of the so-called Guatemalan National Revolutionary Unity (URNG) are still armed, they will gather in eight designated camps within the next few weeks to hand in their weapons to international peace monitors.
Most plan to stay with the URNG when it becomes a political movement, as envisaged in one of the 11 chapters of a peace treaty which took five years to reach. They will thus follow in the footsteps of their Sandinista and FMLN neighbours in Nicaragua and El Salvador.
Although the peace process began five years ago, its speedy conclusion was largely due to an atmosphere of trust created by Mr Arzu, a 51-year- old former travel agent of part-Russian extraction, after he took over last January. The final and most controversial accord was completed only last week when Guatemala's Congress approved the Law of National Reconciliation - a sweeping amnesty that will exempt guerrillas, military officers and anti-guerrilla village militiamen from prosecution for massacres, kidnappings or torture.
The law infuriated local and international human-rights groups who note that, while the guerrillas were often brutal with soldiers or collaborators, it was the military and the militias who were responsible for the majority of the 36-year toll of torture, death and disappearances, mostly of civilians. It will, for example, grant impunity to the officers who carried out a "scorched-earth" policy against alleged guerrilla sympathisers in the Guatemalan highlands, at the height of the war in the Eighties. Using techniques learnt from United States experience against supposed pro- Vietcong villages in Vietnam, the policy involved burning down entire villages suspected of collaborating with, or even of feeding guerrilla units. Also apparently exempt from punishment will be military officers who ordered or carried out the so-called Xaman massacre little over a year ago. An army platoon opened fire on 200 unarmed men, women and children, killing 11 and wounding 30.
The seeds of the 36-year war were sown in 1954 when the CIA helped to overthrow the leftist President Jacobo Arbenz, a coup which led to three decades of military or military-controlled governments. Marxist guerrilla groups were formed, merging into the umbrella URNG, and encouraged by Castro's 1959 revolution to launch their first attacks.
In the early Eighties, the government launched the "scorched earth" policy which sent hundreds of thousands fleeing through jungle to Mexico. Thousands are still there.
The official terrorism campaignworked. The guerrillas lost support and were reduced to blowing up bridges and pylons, as well as extorting "war taxes" from ranchers. That was effectively a protection racket that ensured the guerrillas' survival.
Many Guatemalans fear that some guerrillas will remain outside the law - as some ex-Contra and ex-Sandinista fighters have done in Nicaragua - believing they can live better through extortion than through promised state assistance.