The paper discusses several still unsettled and not systematically investigated questions concerning the situation of Jewish scientists, among them mathematicians, in the Republic of Weimar. Contemporary statements by the well-known leftist and liberal journalists Carl von Ossietzky (1932) and Rudolf Olden (1934) are used to describe the general political situation. A wide-spread feeling of a social and political crisis and changes and perturbations in international scientific communication provide explanatory background for the conditions within academia in the 1920s. A comparison of appointments of Jewish mathematicians to full professorships before and after World War I does not give significant differences. Attitudes of Jewish mathematicians such as Felix Bernstein, Richard Courant, Emil Julius Gumbel, Edmund Landau, Richard von Mises, Johann von Neumann and Adolf A. Fraenkel, but also of non-Jewish mathematicians such as Felix Klein, Walther von Dyck and Theodor Vahlen will be discussed, providing some unpublished material. One statement by Felix Klein (1920), which shows his undecided stance with respect to the problem of anti-Semitism, and an excerpt from Richard von Mises’ diary (1933), where he reflects on his status as a Jewish mathematician and as a refugee, are particularly valuable as points of reference for necessary further research.