Characterization of poliovirus strains by an enzyme immunoassay (EIA). An enzyme immunoassay performed with polyclonal antisera to poliovirus types 1, 2 and 3 absorbed with heterologous strains of the same types was used for the characterization of poliovirus field isolates. The assay allowed the identification of 74 (93.6%) out of 79 isolates as wild or vaccine-like strains. Applications of EIA for the study of polioviruses are discussed.