The spatial and temporal distribution of various trace elements in water and suspended solids in urban runoff from residential and industrial sites was studied. 240 sequential urban runoff samples from 39 rain/storm events were collected, processed and analyzed for 13 elements (12 metals - Al, Co, Cd, Cr, Cu, Fe, Mn, Pb, Ni, Ti, V, and Zn, and one metalloid--As). The experimental protocol used in this study was validated using standard reference material (NIST 1648, urban particulate matter) and certified rain water samples. Good agreement was obtained between the certified and measured values. Al, Fe and Zn were found to be abundant in both residential and industrial runoffs. Some of the metals demonstrated first flush phenomena. Investigation of dissolved fraction, environmentally mobile fraction and total concentration for the 13 elements revealed that trace elements in industrial runoff were highly enriched as compared to those in the residential runoff. The environmentally mobile fraction was quite significant for most of the trace elements. Statistical correlations among the metals were studied, and principal component analysis (PCA) was used for identification of the major sources of the metals/metalloid in both residential and industrial runoffs. Crustal leaching, paints from building walls, and atmospheric deposition were found to be the main sources of metals/metalloid in runoff from the residential site while emissions from petrochemical and semiconductor industries, metal corrosion and vehicular emissions were the main sources of metals/metalloid in runoff from the industrial site. These results are presented and discussed in this paper.