People streamed in their tens and hundreds of thousands through the streets of Bogota, as they demanded an end to kidnappings, killings and lies by Farc rebels.
By the time they reached the main square, in their trademark white T-shirts, some estimates were putting their numbers at between 500,000 and two million.
Farc is believed to be holding some 700 people hostage in miserable conditions. Pictures of some are on display in central Bogota.
Cali is probably best known outside Colombia for lending its name to a drugs cartel. But here too people were ready to protest against the Farc.
Similar protests took place across much of Latin America. In Uruguay, anti-Farc protesters gathered beneath a statue of the iconic liberation hero Simon Bolivar.
Astrid Betancourt, sister of one of the Farc's highest-profile hostages, Ingrid, is in reflective mood as she speaks on a mobile phone at a news conference in Paris.
The anti-Farc revulsion felt in so much of Latin America - and Europe - was also expressed in Spain.