Air quality management in India is being studied with more rigor. A detailed chemical analysis of fine particles helps to identify the sources of pollution and to predict potential health effects and climate change. In the present study, fine particles were measured at four locations in Mumbai city, India, during 2007–2008. The fine particles were measured using MiniVol portable air samplers. After gravimetric measurement, ions, elements, elemental carbon and organic carbon were analyzed. The average PM2.5 mass concentrations at control (C), kerb (K), residential (R) and industrial (I) sites were 69 ± 20, 84 ± 31, 89 ± 33 and 95 ± 36 µg/m3 respectively. The average OC contributions at C, K, R and I sites were 30%, 34%, 35% and 31% respectively while EC contributions were 7%, 11%, 9% and 8% respectively. The non-sea salt contributions of SO42–, K+ and Ca2+ were over 85% suggesting anthropogenic sources. Pb and Zn were highly enriched (> 1000). Reconstruction of mass of PM2.5 in Mumbai city includes organic matter (36–52%), secondary inorganic aerosols (21–27%), crustal (6–12%), noncrustal (4–8%) and sea salt (6–11%). The present study aims to improve the scientific understanding of aerosols.