A diploma thesis is focused on the Czech-German relationships' temper in Brno in the first three decades of the 20th Century. This term is divided into three evolutionary phases. The first phase concentrates on the position of the Czech people in comparison to the position of the German people before 1918. The second phase deals with the direct reactions of the people from both groups and with the general turnover in the society that was caused by political circumstances of the 28th October 1918. The third phase considers national disagreements and on the other hand how the people were able to cooperate with each other. The topics as the educational system, theatre, clubs or architecture are mainly analyzed. For completeness' sake the final part of the thesis is aimed to German language islands that were formed in the town districts and in the south-facing adjacent villages from Brno.