A biochemist at Columbia University, Erwin Chargaff discovered the base-pairing regularities or "complementarity relationships" of nucleic acids that provided one of the key steps in developing a structural model for DNA. During his long career, Chargaff is credited with conclusively falsifying the tetranucleotide hypothesis; demonstrating the existence of a large number of DNA species; and creating the first descriptions of hypochromicity, hyperchromicity, and the denaturation of a DNA. In addition, Chargaff conducted important research on blood coagulation, lipids and lipoproteins, the metabolism of amino acids and inositol, and the biosynthesis of phosphotransferases. He retired to emeritus status in 1974 and remained active in research almost to the time of his death in June 2002. The Chargaff Papers are organized into ten series: I. Correspondence, 1931-1992; Ia. Correspondence, 1949-2002; IIa. Grants, 1930-1982; IIb. Subject Files, 1940-1984; IIc. Subject Files, 1946-2002; III. Works by Chargaff, 1929-1989; IIIa. Works by Chargaff, 1923-2002; IIIb. Reprints, 1977-1999; IV. Works by Others, 1936-1985; IVa. Works by Others, 1976-2002; V. Research Notes and Notebooks, 1929-1951 ; VI. Photographs, 1935-1977; VIa. Photographs, 1928-2002; VII. Audiovisual Materials; VIII. Awards and Certificates, 1958-2001; IX. Lecture Notes, 1942-1985; X. Personal Papers, [1880]-1985.