Weekly PM2.5 samples were collected for one year in Beijing and Shanghai and the crustal elements analyzed to investigate the concentration levels and temporal variations of ambient fine mineral dust. The mass concentrations of Al, Si, Ca, Mg, and Fe exhibited similar significant weekly variations in both Beijing and Shanghai. The annual average PM2.5 concentrations of major crustal elements ranged from 0.27 microg m-3 Mg to 2.48 microg m-3 Si in Beijing, which were 1.40-2.24 times higher than those in Shanghai. Their PM-weighted values were comparable between the two cities. A distinct seasonal pattern was present for these crustal elements with the highest concentrations during the spring in Beijing and during the winter in Shanghai, and the lowest concentrations during the summer in both cities. During the dusty spring of 2000 in Beijing, soil dust was the second most abundant PM2.5 constituent with a contribution as high as 18.6%, over twice that in the winter. The highest fine soil concentration (37.8 microg m-3) and mass percentage (41.6%) occurred in the same week of intensive dust events impacting Beijing. The impact of dust storms complicates the goal of reducing PM2.5 in Beijing. Ca originating from construction activities appears to be a significant PM2.5 contributor as well.