Rotaviruses and noroviruses are the main causes of acute gastroenteritis in young children and adults, respectively. Prospective molecular surveillance of rotavirus genotypes in France and Europe shows that circulating strains may vary with the season, locality or country. Rotavirus OK? genotypes G1 and G9 are the most prevalent. Most strains are associated with P[8], showing a certain genotypic stability of rotaviruses currently circulating in Europe and suggesting that vaccination would be effective at least in the short and medium term. However, atypical strains G12 and G8 must be monitored in case they emerge in future. Noroviruses belong to the Caliciviridae family. These single-stranded RNA viruses show major genetic diversity. they are divided into 5 genogroups, which are themselves subdivided into genotypes. In addition, new variants are continually arising, and are frequently associated with new epidemic waves of gastroenteritis.