The book examines the efforts of the University of Vienna to fight Hussitism in the eventful years between the Councils of Constance (1414-1418) and Basel (1431-1449). Antiheretical actions materialized mainly in two different ways: by administrative and organizational provisions and by theological argumentation. The University obliged its members to abide by the Catholic faith and it supported the military and diplomatic moves of the Austrian Duke, while emphasizing her loyalty to the Roman Church and the papacy. Furthermore, treatises authored by professors of the University argued against Hussite practices and against the Four Articles of Prague. A famous example of such literary support is the widely spread Viennese Tractatus contra quattuor articulos Hussitarum from 1424, which receives a close analysis for the first time.