A study was undertaken from November 1994 to August 1996 to determine the role of viruses in children (less than or equal to 5 years of age) hospitalized at Beijing Children Hospital, Beijing China, for acute diarrhea. Stool samples from diarrheal patients were investigated by ELISA, electron microscopy, and RT-PCR for the presence of rotavirus, calicivirus, astrovirus, and adenovirus. Group A rotavirus was detected in 55.9% of all diarrheal patients and comprised 82.5% of all viruses detected. Group A rotavirus samples were further characterized for their G-type specificity by RT-PCR. Four major G types (1-4) were identified. G1 to G4 accounted for 58.9%, 15.7%, 16.8%, and 6.3%, respectively, of the serotyped samples. Almost all rotavirus infections occurred in children less than 1 year of age, with a significant clustering during the winter months. Group C rotavirus was detected in one 18-month-old child. Astroviruses, caliciviruses, and adenoviruses were detected in 8.5%, 7.6%, and 2.5% of the hospitalized children, respectively. This, the first viral etiological study of childhood diarrhea in China, concludes that rotavirus G1-4 strains play an important role in severe diarrhea in Beijing children. (C) 1999 Wiley-Liss, Inc.