The study was part of the South American Emissions, Megacities and Climate Project (SAEMC). The objective was to identify and quantify organic and elemental carbon (OC and EC), monosaccharides, polycyclic aromatic hydrocarbons (PAHs), oxy and nitro-PAHs, water-soluble ions (WSI), and elements in particulate matter collected in intensive campaigns during a period (June, 2010) in São Paulo (Brazil), Lima (Peru), and Medellín (Colombia). PM10 concentration was higher in São Paulo than in the other two sites and 75% of the samples had concentrations above the World Health Organization (WHO) guideline. High concentrations of levoglucosan, a biomass burning tracer, highlighted the importance of this source in the Brazilian megacity. Levoglucosan-to-mannosan ratios for São Paulo suggested sugarcane burning, which in 2010 occurred in 70% of the state municipalities during harvest. Vehicular-related elements (Fe and Cu) had higher concentrations in São Paulo. As and Pb in Medellín were attributed to industrial emissions. Ni in Lima was associated with emissions from metal smelting facilities and ship heavy oil combustion. Higher total PAH concentrations and benzo[a]pyrene equivalent (BaPE) index in São Paulo indicated a stronger influence of vehicular exhaust in this megacity. The results highlighted the importance of biomass burning and vehicular sources for São Paulo, vehicular exhaust, biomass burning, and industrial sources for Medellín, and marine aerosol, together with vehicular, industrial, and ship exhaust, for Lima.