Five days later, he created the National Commission on the Disappearance of Persons (CONADEP), led by Argentine writer Ernesto Sábato. However, it was also under Alfonsín's presidency that the December 24, 1986 Ley de Punto Final ("Full Stop Law") was voted, granting amnesty to all acts committed before December 10, 1983, amid pressure from the military. It would not be until June 2005's Supreme Court decision to overturn all amnesty laws that investigations could be started again.
During the Alfonsín administration, a Treaty of Peace and Friendship of 1984 between Chile and Argentina with Chile was signed and the roots of the Mercosur trade bloc were established.
In 1985 and 1987, large turnouts for mid-term elections demonstrated continued public support for a strong and vigorous democratic system. The UCR-led government took steps to resolve some of the nation's most pressing problems, including accounting for those who disappeared during military rule, establishing civilian control of the armed forces, and consolidating democratic institutions. One of the biggest achievements of the Alfonsín administration was the reduction of corruption in public offices, which was reduced by half during his administration. However, constant friction with the military, failure to resolve several economic problems inherited from the military dictatorship and great opposition from the labor unions undermined the effectiveness of the Alfonsín government, which left office six months early after Peronist candidate Carlos Saúl Menem won the 1989 presidential elections.