Average ozone concentrations at a remote site in the Uludag Mountain of Northwestern Turkey was 29 ppb for a 12 month period. Only 11% of the time l-h average values exceed 50 ppb. The US Air Quality Standard of 0.12 ppm was not exceeded. The diurnal variations of O-3 and NO2 were 27 and 2.3 ppb respectively, during summer 1993, indicating the impact of urban and industrial sources. Highest O-3 concentrations were observed under southerly and northerly winds, suggestive of the transport of photochemically produced oxidants from Bursa city and industries and a power plant located downwind of the sampling site.