The Mexican report was released online by the US National Security Archive which said it posted the document because Mexicans had a right to know about the extent of state responsibility for killings, disappearances, torture, illegal detention and harassment. The exact period covered is 1964 to 1982.
Serious human rights abuses were committed by the military during that period according to the report including torture, mutilations, beatings and executions.
President Vicente Fox set up an office in 2002 to probe human rights violations under three earlier administrations.
The research was submitted to a special prosecutor on December 15 but has not been officially published in Mexico, although extracts have appeared in the local media.
Kate Doyle, director of the archive's Mexico Project, said that the report was "circulating among a handful of prominent people" but that those most affected by the violence could still not read it.
This "is a state of affairs reminiscent of Mexico's past, when citizens were routinely shut out of civic participation by a government determined to keep them in the dark," she said.
"Information was power, and the right to information did not exist for ordinary Mexican men and women," she said.
"The National Security Archive's commitment to openness has prompted us to make this draft report available to the public in Mexico and across the world."
The archive noted that crimes reported in the draft report were committed "during the administrations of Presidents Diaz Ordaz (1964-70), Echeverria (1970-76) and Lopez Portillo (1976-82).
"In those years, hundreds of Mexican citizens -- innumerable innocent civilians as well as armed militants -- were murdered or 'disappeared' (abducted and presumed killed) by military and security forces.
"Thousands more were tortured, or illegally detained, or subjected to government harassment and surveillance."
The archive is an independent non-governmental research institute and library located at George Washington University in Washington.
Mexico's political violence has not been as thoroughly documented as other countries in Latin America that had oppressive regimes such Argentina and Chile.
The election of Vincente Fox ended more than 70 years of one-party rule in Mexico under the Institutional Revolutionary Party.