The apicomplexan pathogens of Eimeria tenella cause coccidiosis, an intestinal disease of chickens that has a major economic impact on the poultry industry. Members of Apicomplexa share an assortment of unique secretory organelles (rhoptries, micronemes, and dense granules) that mediate invasion of host cells and the formation and modification of the parasitophorous vacuole. Among these, microneme protein 2 from E. tenella (EtMIC2) has a putative function in parasite adhesion to the host cell to initiate the invasion process. To investigate the role of EtMIC2 in host parasite interactions, the production and characterization of 12 monoclonal antibodies (mabs) produced against recombinant EtMIC2 proteins is described. In an immunofluorescence assay, all mabs reacted with molecules belonging to the apical complex of sporozoites and merozoites of E. tenella, E. acervulina, and E. maxima. By Western blot analysis, the mabs identified a developmentally regulated protein of 42 kDa corresponding to EtMIC 2 and cross-reacted with proteins in developmental stages of E. acervulina.