This paper reports on a study of pupils' knowledge and understanding of atmospheric pollution. Specifically, the study is aimed at identifying: 1) the extent to which pupils conceptualise the term "air pollution" in a scientifically appropriate way; 2) pupils' knowledge of air pollution sources and air pollutants; and 3) pupils' knowledge of air pollution consequences. The sample consisted of 132 Greek pupils, aged 7-13 years. Data were collected through semi-structured interviews during which pupils were asked to provide open responses articulating their views concerning issues related to air pollution. The analysis of the data revealed that children have a concrete and generalised conceptualisation of air pollution and air pollutants. Moreover, they are familiar with the anthropogenic sources of air pollution, with the impacts of air pollution on human health, and with the interdependence of this issue with a variety of environmental aspects. The outcomes of the study allow for the formulation of educational implications and suggestions for the discussion of air pollution in the science classroom. (Contains 4 tables.)