Avian coccidiosis, caused by parasites of the genus Eimeria, is a major disease of intensively reared poultry. Anticoccidial drugs, and vaccines based on live wild-type (virulent) parasites, have aided the management of coccidiosis, but the development of vaccines based on live attenuated parasites has been a significant advance. Here, Martin Shirley and Petr Bedrník explain the basis of these recent vaccines and discuss their use.