A review of the literature reveals considerable evidence to support the suggestion that vegetative surfaces remove particulate matter from the atmosphere. Preliminary observations of the leaf surfaces of an important urban tree indicate the presence of numerous particulate contaminants. In view of the medical importance of fine particles in urban atmospheres, it is important to assess the efficiency of tree surfaces in particle retention. Can particulate loads be reduced below biologically significant thresholds by vegetation? Are trees acutely injured or subtly influenced in the process of this removal? A brief assessment of research needs is provided.