Overdiagnosis is now recognized as a common and serious problem in human medicine that causes substantial harm in terms of unnecessary costs, wasted resources, and patient and caregiving suffering. International conferences and special features in major medical journals have been dedicated to discussions of overdiagnosis and overtreatment. In 2012, a consortium of 70 specialty groups created the online resource Choosing Wisely to help physicians and patients make evidence-based decisions that reduce overdiagnosis and overtreatment. Changes in clinical practice guidelines and public education strategies have resulted from the growing recognition of the risk of overdiagnosis in human medicine, including highly publicized changes in recommendations for prostate cancer screening in men and breast cancer screening in women. This review by Dr. McKenzie explores this problem both in human and veterinary medicine and outlines how our profession should start to address an issue of great of importance to clients and clinicians alike.