Abstract:Sol Spiegelman (1914-1983) was an American microbiologist who made several important contributions in the fields of microbial genetics and cancer research, particularly the discovery of RNA/DNA hybridization and the first synthesis of an infectious nucleic acid. Biographical material, correspondence, laboratory notebooks, published and unpublished writings, academic course material, subject files, memoranda, and illustrations document Sol Spiegelman's professional career as a microbiologist.