Conventional drama is also a subject area of literary research. It includes texts covering a whole range of genres, though not all are linked to the traditional medium of theatre let alone dramatic theatre. The operetta libretto is among the special genres. In common usage 'libretto' means the story the operetta is based on. The operetta libretto is a musical-dramatic genre that originated in France in the 1850s. From there it spread to other countries, particularly those of central Europe. In the twentieth century it began to stagnate until by the 1940s it was gradually giving way in the popular theatres to other genres. In the Czech cultural context the libretto developed from simple translations and adaptations of foreign works in the second half of the nineteenth century to strong home-grown works in the 1930s and 1940s but then experienced a radical downturn in the late 1940s and early 1950s. In a section devoted to a morphological analysis the article is concerned chiefly with the libretto of the 1930s and first half of the 1940s. This sort of libretto has three acts, the second of which comes to a climax in a dramatic finale and the third (usually shorter) has the form of a simple denouement. The setting was chosen to allow exotic or folk elements to be suitably linked with salon society. Authors of libretti put particular emphasis on comic effect, which alternated with the merely sentimental. In its dialogues the libretto was marked by a weak relationship between the spoken word and song lyrics (with the exception of the finale). The characters were not conceived as unique but as set types of people with conventional characteristics, particularly in behaviour, thinking, appearance, expression, and content of the spoken dialogues and sung texts. The article concludes that more research is needed on the operetta libretto, because it is a genre that exerted a wide-ranging influence on Czech culture in the nineteenth and twentieth centuries.