Avian coccidiosis is caused by several distinct species of Eimeria protozoa and is the major parasitic disease of poultry of economic importance. As an alternative strategy to control avian coccidiosis without using prophylactic medications, we have investigated the efficacy of inducing passive immunity against coccidiosis by orally feeding hyperimmune IgY antibodies. In this study, a commercially available egg yolk powder, Supracox (SC), a purified IgY fraction of egg yolk prepared from hens hyperimmunized with three major species of Eimeria oocysts, were continuously fed to young chicks from hatch. Upon orally infecting these broiler chicks with Eimeria tenella and Eimeria maxima oocysts at 1 week of age, they showed significantly higher body weight gains (P<0.05) compared to the untreated controls. Furthermore, SC-fed chicks showed significantly less intestinal lesions and reduced fecal oocyst output compared to the untreated controls following oral infections with E. tenella and E. maxima. These results provide clear evidence that passive immunization of chicks with hyperimmune egg yolk IgY antibodies provide significant protection against E. tenella or E. maxima infections.