Diarrhea is a common childhood illness in Myanmar, and rotavirus is the single most important etiological agent of diarrhea. Surveillance for rotavirus diarrhea in children <5 years of age was conducted in a tertiary pediatric hospital in Yangon, Myanmar, from January 2002 through December 2003. Stool specimens obtained from children admitted to the hospital for acute diarrhea were tested for the presence of rotavirus by use of an enzyme-linked immunosorbent assay. Diarrhea was the cause of 5671 (18%) of all hospitalizations of children <5 years of age during the 2-year study period (n = 30,869). Rotavirus was identified in 923 (53%) of the 1736 stool specimens tested, and rotavirus infection was associated with approximately 10% of all hospitalizations of children. Rotavirus diarrhea most frequently occurred in children 6-17 months of age, and it was more commonly identified in boys (62% of children with rotavirus diarrhea were boys). The seasonal pattern of rotavirus disease mimicked that of diarrheal illness due to all causes, with the peak season for rotavirus disease occurring from November through February (i.e., during the cool, dry season). During the study period, 53 of the children who were hospitalized for diarrhea died. The present study confirms the importance of the etiological role that rotavirus plays in childhood diarrhea.