In the 19th century, the concept of 'one medicine' was embraced by leaders in the medical and veterinary medical communities. In the 20th century, collaborative efforts between medicine and veterinary medicine diminished considerably. While there have been some notable exceptions, such as Calvin W. Schwabe's proposal for unifying human and veterinary medicine and joint efforts by the Food and Agriculture Organization and World Health Organization to control zoonotic diseases, 'one medicine' has languished in the modern milieu of clinical care, public health, and biomedical research. Risks of zoonotic disease transmission are rarely discussed in clinical care which is of particular concern if humans and/or animals are immunosuppressed. Physicians and veterinarians should advise their patients and pet-owning clients that some animals should not be pets. The risk of zoonotic disease acquisition can be considerable in the occupational setting. Collaborative efforts in biomedical research could do much to improve human and animal health. As the threat of zoonotic diseases continues to increase in the 21st century, medicine and veterinary medicine must revive 'one medicine' in order to adequately address these challenges. 'One medicine' revival strategies must involve medical and veterinary medical education, clinical care, public health and biomedical research.