The degradations of gaseous toluene (2-20 ppmv) by solar irradiation (solar), solar irradiation and ozone (solar + O3), solar photocatalytic reaction (solar + TiO2) and solar photocatalytic reaction in the presence of ozone (solar + O3 + TiO2) were studied in a pilot plant. The effects of the inlet concentration of toluene, flow rate and relative humidity on the decomposition of toluene were followed. The experimental results showed that the solar process alone did not eliminate a significant amount of toluene. However, the combination of solar irradiation with either O3 or TiO2 improved the decomposition rate of toluene. A significant toluene conversion, at a high toluene inlet concentration, was achieved by the solar + O3 + TiO2 process. Toluene decomposition was found to be affected by the inlet flow rate; a high flow rate resulted in low conversion. The solar + O3 process was found to be more affected by gas relative humidity; the optimal humidity was found to be around 50%. The products from the photo-degradation of toluene were found to be water-soluble organics. The water-soluble organics were found to have high biodegradability. Thus, a post treatment consisting of a washing technique followed by biological treatment can be proposed.