Photon and thermal neutron activation analysis were used to analyze airborne particulate matter obtained during the period January to March of 1984 for up to thirty elements. Elemental concentrations and meteorological data from the Toronto, Ontario area were subjected to factor analysis and the major sources of particulate deduced. Elemental profiles for six sources, viz. crustal soil, automobile exhaust, road salt, refuse incineration, oil combustion and an unidentified arsenic source, were used in a chemical element balance to quantitatively determine the contribution of each source to the ambient aerosol. Re-entrained soil contributed 67%, automobile exhaust contributed 15% and the other sources contributed lesser amounts to the inorganic particulate matter. Particle-size distributions for nine elements, viz. Al, Fe, Sc, As, Br, Cl, Zn, Mn, V, are presented as an argument for the development of receptor models involving particle-size distribution data.