The surface Ozone has been determined to be human risk factor in urban environments, as well as a contributor to the formation of photochemical oxidants. Where the surface ozone is not a primary pollutant (i.e. not emitted directly by human activity), but it is produced through the action of sunlight on primary pollutants such as nitrogen oxides and hydrocarbons. Concentrations of ozone were measured at five monitoring sites located in the greater Cairo area, Egypt, as a part of the air pollution study for the effect of the volatile organic compounds and nitrogen oxides on surface ozone.  For each site, during the period from March 2003 to March 2004, we collected forty eight Ozone samples per day (every half hours), daily samples of nitrogen oxides (Nitrogen oxide & Nitrogen dioxide) and 22 abundant volatile organic compounds (VOCs) three times per day (7-9 in the morning, 2-4 afternoon and 8-10 evening). The average ozone concentrations were found to be higher in the afternoon than in morning and nights.  The morning rush hours are marked by an increase in the primary emission of NO and hydrocarbons. In the evening and night, ozone is destroyed by NO generated locally by unburned hydrocarbons from industry, traffic and thermal power plants.