This issue of Veterinary Clinics: Equine Practice, guest edited by Dr. Robert MacKay in collaboration with Consulting Editor Dr. Thomas Divers, is devoted to Controversies in Equine Medicine and Surgery. Topics in this issue include: Hepatitis viruses in horses; Surgical treatment of wobblers; Electrical nerve stimulation in the management of equine headshaking; Lidocaine in postoperative management of colics; Neonatal encephalopathy; Shared mechanisms in the pathophysiology of different clinical forms of laminitis and implications for prevention and treatment; Toward functional cartilage restoration over chondral and subchondral defects in equine joints: prospects for regenerative medicine; Diagnostic testing for equine endocrine diseases; Treatments for sarcoid; EIPH importance and prevention; Treatment options for equine melanoma; and Removing a placenta.