In this study a modeling system consisting of PSU-NCAR MM5 and CMAQ model has been applied to a summertime high ozone period in Istanbul, Turkey in the framework of COST-728 Action. A comprehensive anthropogenic and model ready emission inventory was developed for the first time to make detailed air quality simulations possible in the region. Although the system is still being tested and developed, the first results were very satisfactory. The model performances are evaluated by comparing the model prediction to the measurements. The results show that the predicted ozone concentrations are close to the measured data at semi urban station of the city. But model predictions are underestimated at a background station on Buyukada (Princess Island) due to its location. The statistical evaluations of the model results showed that the modeling system was capable of capturing the temporal resolution as well as the magnitudes, reasonably well.