Autism is a syndrom with unknown etiology, however many hypothesis are described in medical publications. These hypothesis include clostridial spores as key elements. Exo- and also endogenous spores are possible cause of autism: antibiotics have lack of effects on spores, which germinate after discontinuation of antibiotic therapy to vegetative neurotoxin producing forms. In this paper we discuss possible role of gastrointestinal tract and intestinal microflora in pathomechanism of autism on the light of recent publications.