Based on the study of surviving archive sources avail-able in Czech country and abroad, original professional journals mathematical works, and diverse secondary literature we will introduce the most important and interesting phenomena from the history of Czech and German mathematical communities in Prague at the end of the 19th century and in the first two decades of the 20th century. We will try also to capture their specifics arising from the Prague "genius loci" where two different mathematical communities existed and to signal their link-age to surrounding scientific world.
The role and influence of the World War I in the development of the mathematical communities in Prague as well as their activities are analyzed.