In order to assess the impact of SO2, CO2, NOx, and CO on non-enzymatic foliar defense mechanism around oil refineries, the present study was undertaken in Batman, Turkey during the periods February-April-June 2002. For this purpose, the four common evergreen plants at all sites, Pinus nigra Arn. subsp. pallasiana ( Lamb.) Halmboe, Ligustrum vulgare L., Thuja orientalis L., and Nerium oleander L. were selected as test plants. Four study sites were selected at the Batman Refinery area (AR). Four control sites were also selected at a distance of about 5 km from the refinery ( OR). Responses to oil refinery pollution of plants, heavy metals, chlorophyll (chl), proline, carotenoids, lipid peroxidation, SH-compounds, and ascorbic acid were measured. In addition, ambient pollutant gas concentrations were measured. The pollutant gas concentrations were high in the immediate vicinity of oil refinery. The levels of total chl, SH-compounds, ascorbic acid, and chla/chlb ratio were found to decrease, and the amount of proline, carotenoids, lipid peroxidation, and reduced ascorbate/oxidized ascorbate ratio were found to increase in comparison to plants growing at the control sites. A comparison of four evergreen plant species indicated that L. vulgare was the most resistance to refinery induced air pollution and the magnitude of foliar injury symptoms was greatest in P. nigra and T. orientalis.