This article considers the two major biographies of sexologist Magnus Hirschfeld, MD (1868-1935), an early campaigner for "gay rights" avant la lettre. Like him, his first biographer Charlotte Wolff (1897-1986) was a Jewish doctor who lived and worked in Weimar Republic Berlin and fled Germany when the Nazi regime came to power. When researching Hirschfeld's biography (published in English in 1986) Wolff met a librarian and gay activist, Manfred Herzer, who would eventually be a cofounder of the Gay Museum in Berlin and publish (in German, in 1992) the other major Hirschfeld biography currently available. Using, inter alia, the correspondence between Wolff and Herzer, the article aims to explore and interrogate the boundaries and possibilities of "biography" as a form of "doing history."