We studied antibodies to enteroviruses in four groups of serum specimens: those from healthy adults, cord blood specimens, serum specimens known to contain immunoglobulin M (IgM) to coxsackie B (CB) viruses by radioimmunoassay, and serum specimens from children with symptomatic enteroviral infections. Enzyme-linked immunosorbent assays (ELISAs) were developed to detect the IgG class- and subclass (IgG1, IgG2, IgG3, and IgG4)-specific responses to CB3. The CB3 virus ELISA was not type specific. There was very poor correlation between CB3 virus neutralizing titer and IgG anti-CB3 virus ELISA results, indicating that antibodies to heterologous picornaviruses cross-react with CB3 virus in the assay. All serum specimens tested except one were IgG positive for CB3 virus. All 32 cord serum specimens were positive for IgG1 and IgG3. No enterovirus-specific IgG2 or IgG4 was detected in any serum specimen tested. Most serum specimens from the IgM-positive group, healthy adults, and children with enterovirus infections were positive for IgG1 and IgG3. Class and subclass antibody titers remained constant over time. IgG antibodies to enteroviruses appear to be restricted to the IgG1 and IgG3 subclasses. This pattern is similar to results obtained by other investigators evaluating IgG subclass antibodies to protein antigens.