Coxsackieviruses A are known to cause a wide range of human disease processes. However, because many coxsackieviruses A present in clinical specimens do not produce a recognizable cytopathic effect in readily available tissue culture systems, infections with coxsackieviruses A are often difficult to diagnose. We have thus developed enzyme-linked immunosorbent assay (ELISA) systems for the detection and serotyping of coxsackievirus A antigens. The assays consist of a double-antibody ELISA which utilizes type-specific monkey and mouse coxsackievirus antisera. Although some cross-reactivity was noted, the ELISA systems correctly identified the serotypes of 22 to 23 coxsackievirus A complement fixation antigens available for testing. Testing of tissue culture fluids revealed that antigen could often be detected by ELISA before the appearance of a cytopathic effect. In addition, the infecting coxsackievirus A antigen could be unequivocally identified in 8 of 11 stool specimens obtained from patients with coxsackievirus A infections. The ELISA system might thus represent an important tool in the diagnosis and study of coxsackievirus A infections.