Viral gastroenteritis is a major worldwide public health problem. The number of identified pathogens continues to increase, and characterization of the viral structures and functions must be inexorably pursued. Investigators have made considerable progress toward understanding the mechanisms of virus-cell interactions, host responses, and pathogenesis, but the application of this knowledge to improve disease treatment and prevention awaits further key discoveries. Despite deficiencies in knowledge of many aspects of these important issues, a vaccine for the most important pathogen, rotavirus, has been submitted to the US Food and Drug Administration for approval.