Anomalies in animals and humans have attracted human curiosity for centuries and the literature on this topic is enormous. The rediscovery of hotspots of malformed frogs by school-kids in the USA in 1996 has brought this issue into the spotlight of the media, the public, politics and science. This volume of MERTENSIELLA provides the first comprehensive global review of the occurrence of anomalies in natural populations of amphibians and of the types of anomalies that have been evoked by experimental exposure to the potential causative factors of anomalies in natural populations. It includes a case study of the discovery of one of the most severe global hotspots, including its implication for environmental politics. A comprehensive terminology of amphibian anomalies, including synonymies, and recommendations for the study of anomalies in natural populations provide essential backgrounds for understanding and planning studies on amphibian anomalies. The volume is liberally illustrated with colour photos and facilitates access to more than 1000 publications on amphibian anomalies.