1998) A comparative analysis of mutagenic activities of air samples collected from Riyadh before, during and after the Samples of air particulates were collected from the city of Riyadh in 1988 before the Gulf War, a few months after the torching of oil wells in Kuwait during 1991 and several months (in 1992) after the burning oil wells were fully capped. The air samples were collected on fibre glass filters (GF-A, pore size 1.6 m m) by using a RADECO air sampler. Filters were shredded, soaked and sonicated in acetone to dissolve the organic contents. The solid residues obtained after evaporation of acetone were redissolved in 5 ml volumes of fresh acetone and tested for mutagenic activity in the Ames Salmonella assay using the tester strain TA98 for histidine reversion (Ames 1979, Maron andAmes 1983). The mutagenicity assay was performed with and without metabolic activation provided by the S-9 fraction of an Aroclor-induced rat liver homogenate and co-factors. The results of this study showed that the pre-war samples of air particulates from Riyadh induced 11 histidine revertants/10 m 3 of air analyzed, while the 1991 samples (during war) induced 40 -50 revertants/10 m 3 of air (4 -5 times higher). However, the number of histidine revertants induced by the post-war (1992) samples came down to 10 -11/10 m 3 of air. These data, thus, strongly suggested that there was an increase in air particulate mutagenicity due to the atmospheric pollution of Gulf areas caused by the burning oil wells in Kuwait. This notion is supported by the fact that the mutagenic activity of air samples collected months after the burning oil wells were capped assumed the pre-war level. In view of the strong correlation between mutagenicity and carcinogenicity (McCann and Ames 1976) it would be expected that air pollution with mutagenic agents enhanced by the Gulf War would increase the carcinogenic risk for upper aerodigestive tracts in the exposed population in Kuwait and the surrounding areas. Such adverse health effects of mutagenic air pollutants generated by the burning oil wells in Kuwait should be assessed by proper epidemiologic studies.