In sports competitions, some athletes may resort to doing whatever it takes to win. One of the illicit methods used by endurance athletes to gain an advantage is blood doping. These practices are used to raise an athlete's red blood cell count thus increasing the transportation of oxygen to muscle tissue, resulting higher stamina and performance. Blood transfusion fall into two categories: homologous and autologous. Homologous blood transfusions, where an athlete gets blood from another person, can be detected by flow cytometry. However, autologous blood transfusions, where the transfusions are done by taking the athlete's own blood and refrigerating it until future use, cannot be detected directly. My project has been inspired by this inability to detect autologous blood doping and I am establishing a capillary electrophoresis based method to meet this need. By using capillary electrophoresis, I have developed a method that allows me to distinguish between the clean and doped blood samples. The instrument has numerous advantages over other analytical instruments, including: higher resolution, smaller sample volume requirements, and shorter analysis times. A transfusion can be seen based on the electrophoretic mobility differences of the red blood cells. The difference in the mobility of the cells is the result of the natural aging process of the red blood cells, as well as storage induced changes. In particular the storage of the red blood cells alters the cells size, leading to the mobility differences that we observe. The mobilities differences are even more apparent in athletes as they have fewer old erythrocytes in circulation. As a result, I was able to correctly identify, in vitro doped blood samples, with as little as a 5% transfused blood volume, in 75% of individual tests from sedentary and athletic control volunteers.