This review examines how the Chemical Mass Balance (CMB) receptor model has been used to quantify source contributions from fossil fuel combustion and other sources to ambient concentrations of PM2.5 and PM10 for urban and regional scales. Nonfossil fuel sources, such as fugitive dust, cooking, vegetative burning, and natural or human-caused biogenics must be considered together with fossil-fuel sources in a CMB analysis to obtain closure for PM2.5 and PM10 mass. CMB analyses in 22 different studies have found fossil fuel combustion to be a large contributor to PM2.5 and PM10 concentrations, with most of the primary contributions originating form diesel- and gasoline-powered vehicle exhaust. Primary contributions from ducted sources, such as coal- and oil-fired power stations, are negligible when these facilities have been modernized with effective pollution controls, but they have been shown to be large contributors without these controls. Secondary sulfates and nitrates from fossil fuel combustion are recognized, but their attribution to specific precursor gas emitters is uncertain using either the CMB or source-oriented chemical transport models. Using source and receptor models together improves source contribution estimates and the confidence in those estimates.