This thesis characterizes the mass and chemical composition of the fine particle air pollution over several cities in South Asia and quantifies how major sources impact the observed levels by using Chemical Mass Balance modeling with organic compounds as tracers. During February 1999, as part of the INDOEX program, a study was conducted to measure the size distribution and chemical composition of the fine particles in a remote island in Maldives off the coast of India. We found that the fine particle concentrations were comparable to those found in major cities in the United States, and were surprisingly high for a background site. 10-day backwind trajectories pointed the source region towards the Indian subcontinent; other INDOEX studies confirmed the presence of a thick haze layer over the Indian Ocean and the subcontinent during the time of the experiment. Motivated by these findings, a detailed analysis of ambient PM2.5 was carried out in Delhi, Mumbai, Kolkata, and Chandigarhfour cities located upwind of the island in Maldives. Seasonality of the fine particle concentrations was observed in each of these cities with the highest concentrations occurring during the wintertime and the lowest concentrations during the summer. Size distribution and chemical composition of the fine particle emissions from five Bangladeshi biomass (rice straw, coconut leaves, dried cow dung, synthetic biomass log, and jackfruit wood) and three Asian coals (Bangladeshi, Indian, and Chinese) were characterized and important source signatures were identified. Finally, recently developed chemical tracer techniques were applied to the ambient samples from North India to differentiate between the contributions from the many different source types. The emission profiles and source signatures from the source tests conducted previously along with the ones conducted using the Indian Subcontinent fuels were used as inputs to the model. These results serve several purposes. First, they provide a description of the mass and detailed inorganic and organic chemical characteristics of fine particulate matter conducted for the first time ever in this region. Second, the source apportionment study will help to define the relative importance of those sources that should be included within an air quality control program. Chemical tracer techniques are particularly attractive for application in regions that have not been studied previously because they are able to yield rapid insights into the causes of a local air pollution problem before the completion of an accurate emissions inventory. Third, the source tests results will prove useful in constructing and evaluating regional emission inventory and assessing source impacts on air quality. Fourth, this work has been carried out with collaborations from Georgia Tech and several other Indian research institutions where pollution control personnel in India was trained in the operation of air sampling equipments that were left for continued monitoring, thus contributing to technology transfer and knowledge transfer from the US.