This book is a comprehensive study of the evidential system in German. It presents a systematic description of the encoding of evidentiality in present-day German, as well as a diachronic reconstruction of the relevant sources and paths of grammaticalization from the Old High German period onwards. Based on empirical corpus research, the study investigates the degree of grammaticalization of each single evidential construction and the make-up of the present-day system as well as the diachronic stages that lead to the present state. The book focuses on three main issues. First, it is concerned with the general notion of evidentiality, its deictic character, and with the interrelations between the domains of evidentiality and epistemic modality. Second, the book presents the results of the synchronic corpus-based analysis of the German evidential periphrastic constructions werden 'become' + infinitive, scheinen 'seem', drohen 'threaten', versprechen 'promise' + zu 'to'- infinitive, which constitute a paradigm for coding evidentiality in Present Day German. Third, the diachronic development of the evidential constructions is represented as a complex grammaticalization process, interacting with the development of modal constructions and leading to a highly differentiated category of modal and evidential distinctions in the grammar of German.