Competitive athletes and highly active individuals commonly develop cardiovascular adaptations. Underlying features of exercise-induced cardiac remodeling often manifest as distinct patterns on the 12-lead electrocardiogram (ECG). Considerable effort has been directed toward defining the scope of ECG abnormalities in this population and numerous criteria have been proposed for the task of differentiating benign athletic ECG changes from patterns suggestive of underlying cardiovascular disease. This review will provide a historical overview of athlete ECG criteria development with a final emphasis on remaining areas of scientific and clinical uncertainty.