Henry E. Sigerist (1891-1957) is known as the most influential medical historian in the first half of the 20th century. More than that he was a scholar of an unusually broad spectrum of activities. 50 years after his death he is still the subject of publications. During his active life in Zurich, Leipzig, Baltimore, and again in Switzerland he exchanged letters with some 300 correspondents of all walks of cultural life. The letters to Sigerist as well as the copies of his own letters are preserved in near completeness, a fact that allowed an unabridged and annotated edition. This volume contains Sigerist's correspondences with the architect of American medicine, William H. Welch, the pioneer brain surgeon, Harvey Cushing, the medical bibliographer, Fielding H. Garrison, and the medical historian, Erwin H. Ackerknecht. The letters allow insight into the correspondents' biographies and activities, their private lives, and relationships between persons, topics, and books. They also reflect the eventful time of the mid-20th century. To each of the four correspondences is added an introduction and indices of literary works and of persons mentioned.