The presented thesis is focused on the Radiolaria of the Czech Cretaceous Basin. The studied material was collected in Březno u Loun and in the Úpohlavy quarry. Biology, ecology and morphology, as well as systematics of the whole group is discussed. An important part of this thesis constitutes of the geological settings of Cretaceous, Czech Cretaceous Basin and both localities. 26 samples from Březno and 24 samples from the Úpohlavy quarry have been studied using several methods with the aim to obtain most numerous and best preserved communities possible. Despite poor preservation of the shells, 9 species have been identified. Several shells have been assigned at least to the genus or order levels. Species of Dictyomitra communis (Squinabol, 1904), Dictyomitra cf. napaensis Pessagno, 1976, Turbocapsula cf. giennensis O'Dogherty, 1994, Novixitus cf. mclaughlini Pessagno, 1977, Stichomitra cf. stocki (Campbell & Clark, 1944), Stichomitra communis Squinabol, 1903, Stichomitra japonica (Nakaseko & Nishimura), in Nakaseko et. al., 1979, Holocryptocanium barbui Dumitrica, 1970, cf. Pseudoaulophacus pargueraensis Pessagno, 1963 and genera of Orbiculiforma, Stichomitra, cf. Cryptamphorella have been reported in the Czech Cretaceous Basin for the first time.