Polish Silesia, between 1922 and 1939 was the locus for a model confrontation between three distinct cultural groups of Central European Jews: Jews assimilated to German language and culture, traditional, Yiddish speaking, Orthodox Jews, and still other Jews assimilated to cultures that competed with the originally dominant German one: in the case of Upper Silesia, Polish culture. The linguistic changes these groups experienced are indicative of cultural assimilation and change. All three groups had to respond to a significant emigration of German oriented Jews in the early 1920s, the immigration of Jews assimilated to Polish culture and Yiddish speakers coming from the former Polish Kingdom and Galicia, and an increase in Polish anti-Semitic propaganda in Upper Silesia. A fourth factor was the growing distancing between these Jews and the German state and its direct cultural influences, especially after 1933. A first, and most visible, result of these factors was a rapid rise in declarations of the use of Polish language matched by a rapid fall in declared Germanophones. Initially these declarations were politically motivated: the number declaring Polish its language exceeded by far the actual number of Polish-speakers. By the late 1930s, however, the change was real. Silesian Jews had become essentially Polish speakers, and, on occasion, they had adopted other Polish cultural forms as well. Change of language is thus an important signifier of broader cultural change.