The subject of the dissertation is verification of the mythological information that Matthaeus Praetorius (Matthäus Prätorius) (~ 1635–1704, 1707 (?) circa the second half (end) of the 17th century) recorded in his manuscript “Deliciae Prussicae oder Preussische SchaubĂźhne” (“Deliciae Prussicae or Prussian Theater”). The scholars specializing in pre-Christian Baltic religion and mythology (BRM) used the mythological data provided by the latter source very commonly in the 19th to 21st century, have been using them currently, and are likely do so in the future. However, the reliability of these data has been considered either fragmentarily, or almost not considered at all. The question of the reliability of the mythological information in the “Deliciae Prussicae” has been considered by previous researchers either fragmentarily, or almost not considered at all. Therefore, it makes sense to try and find out the authenticity tendencies of the mythological information recorded in the “Deliciae Prussicae”. In verifying Praetorius’ material, much attention was paid to interdisciplinarity. The study introduces a new term (“information noise”) (“IN”) into the process of verification of the ancient written sources that have recorded the pre-Christian BRM to define informational inconsistencies that arise in the works written in a compilation style. The results of the analysis suggest that the IN that has been sensed in the “Deliciae Prussicae” potentially influenced the development of Lithuanian mythology in the 19th to 21st century. The research carried out has also confirmed that Matthaeus Praetorius is to be regarded as an interpreter, reconstructor and verifier of BRM of the second half (end) of the 17th century. In working on the “Deliciae Prussicae”, he operated access to several unequal levels of mythological material: information from previous written sources; material recorded from the contemporaries. The results of the research suggest that the author of the work under discussion in person observed and / or received information through intermediaries about two different behaviors of the presenters, which he evaluated and compared with each other. Matthaeus Praetorius rewrites the material from the sources recorded by his precursors not only by re-reading it, but also by interpreting it in a particular way. Thus, the verification of the mythological data carried out in the dissertation has allowed the formulation of the five most essential “features of the interpretative system” of the spoken author. The analysis of the “Deliciae Prussicae” has also tracked the tendency of unequal (ambivalent) reliability of the mythological data. The mythological data provided by Praetorius contains a number of references supposing that, in recording the material from the contemporaries, he sought to protect both the presenter and collector of the material from the clerical sanctions for “incorrect religious practices” that were characteristic of the spoken time period, and thus, used the “random action formula” (RAF) consisting of the following three random elements: time, place, and presenter. Finally an overview and assessment of the interpretations made by the 19th to 21st century researchers who studied the mythological material provided by Praetorius has revealed that they used and interpreted the mythological information of the verifiable source in different ways.