We examined the chemical composition of the suspended particulate matter in a typical, middle-sized, nonindustrial Italian town in terms of total carcinogenic PAH, heavy metal, and polynuclear azo-aromatic compounds. The chemical data relate to the biological activity of the organic extract of the particulate matter (mutagenicity and mice alveolar macrophage phagocytosis inhibition). The concentration values of benz(a)pyrene, the concentration ratios of selected PAH's, and the GC-MS profile of some typical samples indicate that motor vehicle traffic is the main pollution source. PAH concentration is significantly correlated with mutagenicity and a phagocytosis inhibition of up to 75% was observed at the highest PAH concentration. As far as the effect of meteorological variables on PAH concentration and mutagen-icity is concerned, a statistically significant inverse correlation with temperature was found.