In a prospective study during the summer and fall of 1982, enterovirus was isolated from 48 hospitalized children; in 29 (60%) enterovirus was isolated from CSF or blood, and in 19 (40%) only a presumptive diagnosis was established. Blood was positive in 21 (44%) and was the only positive specimen in two children. A presumptive diagnosis was provided within 4 days of admission in 38 (80%) and within 48 hours in 19 (40%) of the children from whom enterovirus was isolated. Viremia was most often detected in febrile infants younger than 3 months of age with a clinical picture simulating bacterial sepsis. The presence of viremia was inversely related to the presence of CSF pleocytosis and to virus isolation from CSF. The diagnosis of diseases caused by enterovirus is more accurate when blood culture is added to CSF stool and throat cultures.