This study examines different aspects of language variation in contemporary Czech television discourse. The modern Czech language is characterised by a specific linguistic situation in which speakers must choose between two varieties – Standard Czech (SC) and Common Czech (CC). This choice depends on a number of linguistic, cultural, social and other factors. Television discourse, which is a mixture of prepared and unprepared speech, provides a good opportunity to study the distribution of these varieties and their function. The aim of the dissertation is to research these issues in talk shows and discussion programmes. The following aspects are analysed in the dissertation: – The frequency of occurrence of a number of phonological and morphological elements of the two varieties. This analysis is conducted in a quantitative study of a corpus of 24,000 words (fifteen television shows). The elements are categorised and analysed statistically. The frequency of these elements is shown on two levels: in the total corpus material and in groups of programmes. The results are compared with previous studies of spoken Czech. – A comparative study of the Communist and post-Communist television discourse, in which television programmes from before and after 1989 are analysed and compared. The study reveals a number of linguistic differences between the two programmes and their relation to such factors as operational roles, the function of media and the frequency of dialogue markers. – A qualitative analysis of the fifteen programmes which comprise the corpus. The aim of this study is to show the function of the two Czech varieties in different types of television discourse. The variables affecting the participants’ choice of variety are analysed. The investigation shows that dialogue form, genre and operational roles are directly related to the choice of SC and CC in the programmes. These results are also connected with language norms and other social factors.