Five explicit objectives were established for this study of air pollution climatology in the Kuala Lumpur - Petaling Jaya area. They were: (1) to describe the local climate of the area and its likely implications on air pollution; (2) to examine the rate and nature of emissions occurring in the study area; (3) to attempt to establish the general level of concentrations of selected pollutants; (4) to investigate the influence of local weather factors on pollution concentration and dispersion; and (5) to examine the possible impact of air pollution and urbanization on climatic parameters. Data were collected in Malaysia during 1975-76. Total fuels supplied by the various oil companies were used to estimate air pollution emissions; the Factory and Machinery Department supplied data on dustfall at Batu Caves and the SO₂ in Petaling Jaya. Respirable dust particulates were obtained using the gravimetric dust sampler. Along with the Weld Reservoir Station which was set up specifically for the study, climate data were provided by the Meteorological Service, the Drainage and Irrigation Department, and the University of Malaya. Analyses of these data showed that: (1) On the basis of standard application of U.S. derived forecasting technique, the Kuala Lumpur - Petaling Jaya climate had a great potential for air pollution; (2) Transport, particularly motor vehicles, and industries represent the two most important sources of air pollution. Together they produce 99.3 percent of the major pollutant emissions. Emissions from aircraft, tin mining activities and waste disposals are relatively insignificant. This, and examination of pollutants emitted suggests that Kuala Lumpur - Fetaling Jaya is subject to the Los Angeles type pollution; (3). Computation of total emissions and comparison of these figures with those obtained from other cities suggests that pollution in the study area is of the same order as low to moderately polluted mid-latitude cities. However marked increases in energy use have occurred recently. This, coupled with climate which is characteristically high in air pollution potential, is certainly a cause for concern; (4) Levels of measured air pollution vary in seriousness from one locality to another within the study area. The average concentration of dustfall in Batu Caves area already far exceeded the standard recommended for residential and light industrial areas. Indeed, some stations had even exceeded that recommended for heavy industrial regions. The monthly values of SO₂ at and around the Malayan Acid Works in Petaling Jaya had also on occasions exceeded the accepted levels for human health and vegetation. In both cases, the distribution appears to be related to prevailing wind direction; in the case of SO₂, scavenging effect from precipitation is also significant in reducing concentration; (5) Respirable dust particulate concentrations vary within the study area. In the centre of Kuala Lumpur and in industrial area of Petaling Jaya, these are relatively high. Contrary to results obtained in several mid-latitude cities, seasonal variations and episodic type occurrences of pollution are not evident in Kuala Lumpur. The influence of weather factors upon respirable dust particulates is largely inconclusive; and (6) Like many large urban, Kuala Lumpur - Petaling Jaya has a considerable climate; the degree to which this influences climatic parameters however varies with each climatic variable.