Objective: To describe the clinical course of a dog with a pheochromocytoma multisystem crisis that exhibited autoresuscitation after cardiac arrest. Case Summary: An approximately 10-year-old male neutered terrier mix dog presented for collapse. Abdominal imaging was suggestive of a pheochromocytoma, and clinical pathology data and thoracic imaging suggested the presence of a multisystem crisis. The dog developed cardiopulmonary arrest that was followed by autoresuscitation. New or Unique Information Provided:To the authors' knowledge, this is the first report of autoresuscitation in a dog. The phenomenon may have been associated with a pheochromocytoma multisystem crisis. K E Y W O R D Scanine, Lazarus phenomenon, return of spontaneous circulation INTRODUCTIONAutoresuscitation, also known as delayed return of spontaneous circulation (ROSC) or the Lazarus phenomenon, is the unassisted ROSC after cardiac arrest. 1 Autoresuscitation in people was first described in 1982; it is considered to be an exceptionally rare phenomenon, with a reported incidence of 5.95/1,000 in out-of-hospital cardiac arrest. 2The authors of a meta-analysis published in 2015 identified approximately 45 human cases that occurred after futile CPR or after life support was discontinued, and those patients were clinically dead for a range of seconds to 7 minutes before autoresuscitation occurred. Additionally, 3 patients recovered fully with minimal impairments, 1 recovered with severe impairments, and the rest died anywhere from seconds after autoresuscitation to up to 34 days later. 3 The dog in this report had a pheochromocytoma and exhibited features of a metabolic crisis secondary to that tumor. Pheochromocytomas are tumors of neuroectoderm chromaffin cells of the adrenal medulla that secrete catecholamines. Considered uncom-