This study deals with the seasonal distribution of Al, Ca, Cu, Fe, K, Mg, Na, Pb and Zn and water soluble ions (Cl-, PO43-, NO 3-, SO42-, HCOO-, CH 3COO-, oxalate, succinate, Na+, NH 4+, K+, Mg2+ and Ca2+) found in PM10 samples (particulate matter less than 10 mm in diameter) São Paulo City, Brazil, (April 2003-May 2004). Higher atmospheric levels were found for SO42-, NO3-, Cl- and PO 43- while the main organic anions were oxalate and formate. Atmospheric levels for elements were: Fe > Al > Ca > K > Na > Mg > Zn > Cu > Pb. Some sources were predominant for some species: (i) fuel burning and/or biomass burning (NO3-, HCOO-, C2O42-, K+, Mg2+, Ca2+, Fe, Pb, Zn, Al, Ca, K and Mg), (ii) gas-to-particle conversion (SO42- and NH4+) and (iii) sea salt spray (Cl-, Na+ and Na). © 2012 Sociedade Brasileira de Quimica.