The work carried out at the Institute for Medical Research and lndustrial Hygiene in the field of indoor and outdoor air pollution is reviewed, with particular reference to the development of methods for the determination of very low concentrations of air pollutants, to the studies of the mechanism of reactions, and to the interferences of other atmospheric components in the quantitative analysis of air pollution. Personal protective devices developed at the Institute are described as well. The review also includes the results of the air pollution studies of the atmosphere of the City of Zagreb conducted in the last 6 years.