Surface ozone (O₃) and its precursor’s gases (nitrogen monoxide (NO), nitrogen dioxide (NO₂), nitrogen oxides (NO_x), carbon monoxide (CO), methane (CH₄) and non-methane hydrocarbons (NMHCs), and sulfur dioxide (SO₂) were measured in Yanbu, Saudi Arabia from January 2004-December 2004. The annual average concentrations of O₃, NO, NO₂, NOx, SO₂, CO, CH₄, TNMHCs and THC were 22.51 ppb, 15.58 ppb, 17.25 ppb, 23.84 ppb, 6.66 ppb, 165.13 ppb, 3.44 ppm, 0.56 ppm and 3.88 ppm, respectively. The SO₂/NO_x and SO₂/NO₂ concentration ratios during the period of study indicate that the mobile emissions are the predominant sources in yanbu. The diurnal cycles of O₃ concentrations revealed highest levels in the daytime and lowest levels in night time. The diurnal variations of NO, NO₂, NO_x, SO₂, CO, NMHCs concentrations were similar and showed peaks concentrations linked to traffic density, boundary layer mixing processes and chemical processes in the atmosphere. The mean concentrations of O₃ in different seasons follow the order of summer > spring > autumn > winter. In contrary to O₃, NO has higher concentrations in autumn and winter than those in summer and spring seasons. The highest concentrations of NO₂, NO_x, SO₂, CO, and TNMHCs were found in autumn and spring, whereas the lowest concentrations were found in summer and winter. THC and CH₄ have no significant change over winter, autumn and summer seasons, while their concentrations decrease sharply in spring. Although the studied area does not suffer from NO₂, O₃, SO₂ and CO pollution and no health risk, comprehensive and long-term air quality management programmes are needed in order to keep air quality in a good condition.