The etiologies and pathologies of disorders of sex development of humans and animals explored by integrative approaches at the interface of several disciplines are relevant for fundamental biology as well as human and veterinary medicine. This special issue of Sexual Development presents expert reviews and previously unpublished research that detail the state-of-the-art understanding of the occurrence of abnormal genetic, gonadal and phenotypic sex of livestock and wild and captive-bred exotic animals. Providing insights into the fascinating and medically relevant causes and effects of disorders of sex development this issue is a valuable resource for researchers, clinicians as well as students of biology, animal production, agricultural sciences, human and veterinary medicine.