Each of the three parts of the present thesis treats one aspect of researching Antonio Caldara's masses written in Prague. Chapter One maps the current state of research and relevant basic sources on the Czech territory. Chapter Two focuses on a detailed description and following collations of Caldara's seven masses, quite exceptionally obtained from the musical collection of the Knights of the Cross with the Red Star, with other concordant sources. Examples of watermarks and manuscripts can be found in the Attachment. The partial analysis of selected masses described in Chapter Three serves as a complement to the research of sources. Much attention is given to the macro-structural division of mass compositions in relation to the liturgy.