A total of 209 stool samples were collected from pediatric patients admitted for acute gastroenteritis in a hospital in Hong Kong, during an 8-month period from January to August 2008, and were tested for the presence of rotavirus, norovirus, sapovirus, adenovirus, and astrovirus using a multiplex RT-PCR assay. The most common virus was rotavirus group A (59 of 209, 28%, mainly serotypes G1, G2, G3, and G9), followed by norovirus group II (48 of 209, 23%), adenovirus (7 of 209, 3%, serotypes 2, 3, and 41), and sapovirus (2 of 209, 1%). Interestingly, none of the specimens in this study were positive for astrovirus. One sample was found to have a dual infection with both norovirus group II and adenovirus. The results support the importance of norovirus as a causative agent of diarrhea in children, which may be underestimated by the current routine diagnostic testing.