This chapter, based primarily on ethnographic fi eldwork conducted in 2003/2004 and on follow-up research in 2007, focuses on the peculiarities of the Czech psytrance scene: a small community of a few hundred regular partygoers.1 In my experience the Czech scene offers scarce material for more popular trends in international psytrance-related studies focusing on topics such as spirituality and activism (e.g., Greener and Hollands 2006; St John 2004; Taylor 2001). Rather, the parties in my research provided in the fi rst place carnivalesque breeding grounds for a specifi c kind of psychedelic humour, which was self-consciously associated with a metaphorical state of madness. Demence was the widely used expression for the designation of specifi c drug-induced experiences and outward behaviour patterns of the participants. This ritualised dementia accomplished the temporary demolition and perversion of cultural systems, carried out through cognitive acts, and powered by sensory hallucinations. Most noticeably articulated through verbal communication, the demented vibe was characterised by eclectic playfulness and humorous ambiguity. The fi rst four sections of this chapter offer a comprehensive symbolic analysis. The nonsensical logic inherent in the linguistic projection of demence is explored with references to Lewis Carroll’s Alice’s Adventures in Wonderland. After discussing the relations between demence and the cultural systems of the everyday, the psychedelic-demented experience is further examined within the framework of the party as ritual. This ritual constructs an indeterminate hyperillusion of the world through an excess of simulacra. The fi fth section, borrowing its key concept of grotesque realism from literary theory and re-evaluating the connection with literary nonsense, provides a brief overview of the aesthetic sensibilities triggered by the demented party.