Oil shale ( OS) is one of the world's most important energy resources, and its use can be traced back to ancient times. The objective of this study is to investigate many aspects of OS as an alternative energy source in Turkey, giving Turkey's OS deposits, the history of oil in Turkey, and some studies conducted to evaluate OSs. Research into the utilization of Turkish OSs has been going on since the 1970s, while OSs comprise the second largest solid fuel deposit in Turkey after lignites. OS deposits in Turkey are widely distributed in middle and western Anatolia, with an estimated current reserve of approximately 1,865 million tons. Other potential areas in the north Anatolian fault zone are also under investigation. With the continuing decline of petroleum supplies, accompanied by increasing costs of petroleum-based products, OS may present opportunities for supplying some of Turkey's fossil energy needs in the years ahead.