The article is devoted to the phenomena of metatheatricality, metadramaticality, and metatextuality in drama, without which there is no discussion of 20th century dramatic works, especially the avant-garde and experimental trend in drama. It includes the presentation of the state of research, an attempt to put the terminological chaos in order, and the authoress' proposition to posit the issues in question. Starting point of the paper is the distinction between metatheatricality and metatextuality: the authoress uses the former term to multiplication of levels of the presented world, and the latter term to the actions referring to the body of the text. Resorting to three dramas - Slowacki's 'Kordian', Krasinski's 'Undivine Comedy', and Rozewicz's 'The Interrupted Act' - the authoress demonstrates the various forms of metatextuality and metatheatricality and their mutual relations. Their existence in the drama brings about transformations of the parts of the presented world and dramatic discourse. The drama loses its character of a self-presenting, well constructed machine as Peter Szondi wanted to see it; now rather so-called actions of the subject of the text and conventionality of the presented matter are highlighted. The dramatist is viewed from behind the presented world, puts different masks on, and indicates his/her causation which, due to 'meta' techniques, is constantly put into ironic inverted commas.