Three Parascaris equorum antigens were evaluated in diagnosis of current infection with P. equorum in foals' sera using enzyme linked immunosorbant assay (ELISA) technique. The excretory-secretory antigen (ES) showed marked potency than the crude and egg antigens in diagnosis of P. equorum infection, even that was mixed with other parasites. The electrophoretic make-up of the antigens, examined by sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS-PAGE), revealed different patterns of separation. Most of the polypeptides of ES antigen were immunoreactive in enzyme linked immunotransfer blot (EITB) with P. equorum infected foals' sera and, in the meantime, more than that were recognized in crude and egg antigens. Those polypeptides might be reinforced the sensitivity of ES antigen to be higher than that of other tested antigens in detection of anti- P. equorum antibodies as observed in ELISA test. Those observations were extended by detection specific polypeptide band of P. equorum ES antigen using EITB. Where, from several polypeptides showed reactivity toward P. equorum infected foals' sera, the 28 KDa polypeptide was the only band that was not recognized with the other heterologous sera resuming a specific polypeptide band.