The electron microscopic investigation of biological materials (faeces, intestinal mucous biopsies) from 19 children and sucklings with clinically diagnosed acute gastroenteritis evidenced the presence of some rotavirus-like viral particles in 31 percent of cases. The age of hospitalized subjects varied between 4 months and three years. There have been identified viral particles in the cytoplasm of enterocytes of the intestinal villi and in suspensions of the fecal materials.