Some veterinary practices offer ‘stem cell’ therapy for cats and dogs for the treatment of a wide range of conditions, including arthritis, hip dysplasia, tendinopathy, skin disease and inflammatory bowel disease. But how much has the evidence moved on? This module explains the forms of therapy available, why ‘stem cell’ therapy is now considered a misnomer, how the therapy is regulated, and what is known about its efficacy and safety in cats and dogs.