With a population over 13 million Istanbul is the largest city in Europe. Traffic congestion is by far the most important problem that lessens the quality of life of the residents. Currently 1.8 million automobiles choke its roads daily. The rapid increase in motor vehicles, more than eightfold since 1980, has coincided with a dramatic population and economic growth. As a result, Istanbul is now overwhelmed by a flood of people and vehicles, an inadequate road network and a public transport system that has been slow to develop. This paper presents an overall evaluation of the Bus Rapid Transit (BRT) System in Istanbul of which the first phase was opened in 2007 as a relatively high-speed, high-capacity public transport mode along one of the most congested traffic arterials in the city. Presently it carries about 600,000 passengers daily over a 44 km-long alignment with 33 stations. The paper focuses on system components and presents a comparison with some major BRT systems in the world. Moreover, operational characteristics of travel patterns and ridership are analyzed with the data collected from the surveys and operator of the system; Istanbul Electricity, Tramway and Tunnel General Management (IETT). This study concludes that although the Istanbul BRT System has some drawbacks regarding the running way, access to stations, fare structure and overloaded buses, it has resulted in considerable savings in commuters' travel time and CO2 emissions. Finally, some suggestions for solving the important problems of the system are presented.