The contributions by an international group of leading scholars discuss the historical and cultural relations of old and modern Turkic and Iranian languages. A main topic is how contacts of spoken and written languages from pre-Islamic times until various periods of the Islamic era have influenced the emergence and development of Iranian and Turkic varieties. The purpose is to contribute to a better understanding of the interrelations between cultural-historical contacts and linguistic processes, and to stress the necessity of cooperation between experts of Turkic and Iranian studies.