My contribution focuses on the difficulty of defining and classifying the various forms of the documentary film in different media environments. My argument consists of three central points:1. An essentialist definition of the documentary (for example as the opposite of fictional film) leads us into a trap, as this kind of definition is closely linked to the idea of an inherent structure underlying all documentary films. Hence, this creates misunderstandings, or insufficient notions such as »hybridization.«2. In the theoretical discourse on documentary film, we can observe a shift from essentialist definitions to observations of procedures of reading, producing or even distributing the documentary. These procedures also mark a difference to fictional genres.3. The central criterion for the documentary is the stability of its reference to reality. Therefore, the most obvious way to classify the different forms of documentary films is an analysis of the variance of this stability due to the play of various actors in different milieus.