From c. 1215 to 1368 China was part of the world empire of the Mongols, and during this period underwent many changes as the country was opened up to external influences - demographic, linguistic, religious, socio-economic. The studies by Herbert Franke collected here examine different aspects of this process, dealing with the polyethnicity of China under a dynasty of conquest and the cultural and political roles of non-Chinese, as well as the Chinese reaction, and antagonism to the situation. Of the articles, the first focus on source material, then on the position of the Mongol rulers, tracing their transformation from tribal chieftains into universal emperors, and gods. The following pieces look at cultural contacts, including the author's well-known survey of Sino-Western encounters, while the final ones use biographical studies to illuminate different aspects of Yüan China.