A determination was made as to whether the solvent extract of airborne particles collected locally could induce sister chromatid exchange (SCE) in-vitro and in-vivo in mouse bone marrow and spleen cells. The same extract was also tested for its genotoxicity in Salmonella typhimurium using the Ames assay. In-vitro, mouse bone marrow and spleen cells showed SCE frequency increasing with increasing doses of airborne particulate extract. At the highest concentration tested, 16.09 milligrams/5 milliliters of culture, a toxic effect was noted in both bone marrow and spleen cell cultures. These findings demonstrate that the extract in question induced SCEs in both bone marrow and spleen cells in primary cell culture. In addition these cell types were equally sensitive to the genotoxic effects of airborne particulates. The induction of SCEs in cell culture in the absence of metabolic activation suggests the presence of direct acting mutagens in the airborne particle extract studied. In-vivo, airborne particle extract did not induce significant increases in SCE levels over controls in either bone marrow or spleen cells. This was true in both intraperitoneal injection and oral gavage at different concentrations of extract. These negative findings may be due to inactivation of mutagenic compounds in the body, the inability of mutagenic compounds to reach the bone marrow and spleen, or the inability of relatively low concentrations of mutagenic material in these organs to cause significant increases in SCE levels. The authors point out that the amount and type of mutagens in airborne particles may vary with environmental and meteorological conditions.