Norovirus (NoV) infections that cause acute gastroenteritis are commonly observed during colder months. This study was conducted to investigate the clinical features and molecular epidemiology of NoVs in adult outpatients with acute gastroenteritis in Beijing, China from August 2008 to July 2009. Five hundred nineteen patients were enrolled, their stool specimens were collected, and 136 (26.2%) were positive for NoV. The elderly were found to be more susceptible to NoVs than other age groups. The greatest number of gastroenteritis cases associated with occurred in October. Six GI and eleven GII NoV genotypes were isolated; among these, the GII.4 genotype was most prevalent (70/140 and 50% were the 2006b variant). The elderly were more susceptible to the GII.4 genotype than to other genotypes. Greater numbers of neutrophils in the peripheral blood were observed in the NoV infected group than in uninfected control group. However, the levels of neutrophils and leukocytes in the non-GII.4 patients infected with NoV were higher than those of the GII.4-infected patients. The data highlight the role of NoV as a primary agent responsible for gastroenteritis in adults in Beijing, China. J. Med. Virol. 86:1235-1242, 2014. (c) 2014 Wiley Periodicals, Inc.