Enteroviruses accountfor an estimated 10-15 million symptomatic infections in the United States each year (1). At present, 66 serotypes of enteroviruses are recognized, including three poliovirus serotypes (2). A range of diseases is associated with nonpolio enterovirus infections, including aseptic meningitis, encephalitis, neonatal enteroviral disease, myocarditis, pericarditis, chronic infections among persons with compromised immune systems, poliomyelitis-like illness, hand-foot-and-mouth disease, nonspecific upper respiratory disease, and other manifestations (3). This report summarizes data from the National Enterovirus Surveillance System (NESS) and describes temporal trends of reported enterovirus infections in the United States during 1997-1999.