The combustion of crude oil produces a wide range of pollutants, including gases, volatile organic compounds, polycyclic aromatic hydrocarbons, acid compounds (e.g., sulfuric acid), and soot. Several of these pollutants have been linked with the deterioration and blackening of monuments. The paper reports the results of an investigation on the causes of the soiling of cultural remains at important archaeological sites in the provinces of Khuzestan and Fars, in southern Iran, assumed to be an effect of the Persian Gulf oil well fires of 1991. Different analytical techniques were applied to characterize the mineralogical composition of the damage layers, investigate the deposition of atmospheric particles, measure the anion concentrations, and identify and quantify the carbon components. The results showed that the black deposits on the surfaces of the Iranian monuments considered are mainly microbiotic crusts produced by cyanobacterial growth. No evidence was found of the deposition of particulate matter (smoke) produced by the Kuwait oil fires during the Gulf War.