Rotavirus has emerged as the major enteric pathogen causing acute diarrhea in young children throughout the world. Other viral pathogens have been recognized and additional candidate agents are suspected but none approaches rotavirus in its global impact. A strong appropriate emphasis has been placed on preventive therapy. Although vaccines are not yet available, it is clear that improved hygienic practices, particularly in pediatric institutions, and breast feeding can do much to prevent serious illness during the early months when babies are so vulnerable. During the past decade, from clinical studies and animal models, much has been learned about the pathogenesis of rotavirus diarrhea. These findings provide a sound basis for the use of rational oral fluid therapy, early feeding, and avoidance of drugs during active management. Among the many challenges that remain are the elucidation of the full spectrum of enteric viral pathogens, their impact on man, and their prevention and active therapy.