Elevated levels of ozone [O₃] are becoming a cause of global concern. Ozone in the troposphere near the ground is damaging to plants and materials and harmful to human health. This study was aimed to evaluate level of tropospheric ozone and its precursors and to study the different factors leading to O₃ exceeding levels. Ambient concentrations of O₃, nitrogen dioxide [NO₂] and volatile organic compounds [VOCs] were measured during the summer months of year 2000 at different locations in Alexandria City. Maximum concentrations of O₃ was obtained during the afternoon period of the day because of the photochemical oxidation process in the presence of ultraviolet solar radiation and high levels of O₃-forming pollutants. During weekends, levels of O₃ were lower than that during weekdays at all sampling sites. It was found that activity of an area and its nature has a considerable role in the formation of tropospheric O₃ and its precursors. All levels of O₃ either obtained during the noon rush hour period or during weekdays were below the recommended exposure standards [120 µg/m³] as set in the Egyptian Environmental Law No.4 for 1994.