From 1970 to 1979 the viral laboratory at the Nassau County Medical Center (NCMC) tested 602 culture specimens that were positive for group B coxsackievirus. Eighty-one of the specimens were from hospitalized infants younger than three months of age with nonfatal infection. The case histories of 77 of these infants, whose medical records were available for study, are reviewed here. Aseptic meningitis was the clinical syndrome seen most frequently (48 of 77 patients). Protein levels in cerebrospinal fluid (CSF) did not rise above 170 mg/dl, and in only three infants did the glucose concentration in CSF fall below 30 mg/dl. Infants were febrile for an average of 3.1 days, and no infant had fever of longer than six days' duration. During 1970-1981, eight newborns whose culture specimens were examined at NCMC died of overwhelming group B coxsackievirus disease. The clinical histories of these eight patients and 33 other fatal cases reported in the literature are reviewed. Three patterns of death were observed. Rapid death occurred in 12 patients aged 2-17 days. In 11 patients a diphasic illness led to death at age 8-24 days. In 18 patients a progressive illness was described. Myocarditis was present in all infants. Pulmonary hemorrhage and liver necrosis occurred in 30 and 18 patients, respectively. Jaundice was more frequently observed in fatal cases. Bleeding diatheses were also reported and probably reflect hepatic necrosis. Twenty-four mothers had evidence of a viral-like infection occurring between 10 days antepartum and five days postpartum. Group B coxsackievirus infection must be considered a serious disease of the newborn, which in our community occurred in 77 of 153,250 live births and accounted for six deaths between 1970 and 1979.