Joseph Franz Rock (1884–1962), born in Vienna and later a resident of Hawaii, was well known as a botanist, geographer, philologist and linguist. From 1922 to 1949 he lived in China, where he studied the language and culture of the Na-khi, a people living in Yunnan between the Han Chinese and the Tibetans. Through his research, he became acquainted with the Tibetologist and Mongolist Johannes Schubert (1896–1976), librarian at the University of Leipzig and later professor at the Eastern Asian Institute of the same university. They corresponded quite extensively for over a quarter of a century. Schubert´s estate included almost all of Rock´s letters to Schubert, as well as a number of copies of his own letters to Rock. Rock´s letters give a vivid picture of his long stay among the Na-khi people, of his scientific research, and–following his flight from China in 1949–of his restless later life and his travels in Asia, America and Europe. A lot too can be learned about Schubert´s research from his letters, but also about the often adverse conditions for his Tibetological work, which as a librarian at the University of Leipzig he was for the most part only able to do in his leisure time, and later–in the GDR–under circumstances that were not always conducive to scientific research. The edition also contains a comprehensive bibliography and an index of the persons mentioned in the letters.