The purpose of this review article is to outline the effects of several functional genes/proteins including erythropoietin, vascular endothelial growth factor, hypoxia-induced factor, angiotensin-converting enzyme, peroxisome proliferator-activated receptor gamma coactivator 1-alpha, peroxisome proliferator-activated receptor delta, and phosphoenolpyruvate carboxykinase on endurance performance. These genes, if used properly, can help identify future elite athletes. However, they can also be abused as a way of gene doping.