This is the proceedings of the Second International Conference on Urban Air Quality - Measurement, Modelling and Management, held at the Technical University of Madrid, 3-5 March 1999. This volume contains peer-reviewed papers on the latest advances in the urban air quality research field. It should be suitable for researchers including students, consultants, local authority officers (such as environmental officers), and environmental scientists working in industrial sectors (chemical, environmental, and transport). Very few scientific international conferences specifically address the area of air pollution in cities and towns. This is despite the growing concern about the health and environmental impacts that result from air pollutants in urban areas. The need to have a forum for discussing and exchanging scientific results in this field is hence overwhelming. It is clear from the response of scientists and other experts working in this area that these UAQ conferences are helping to address this need.