Patients will undergo a medical history and general assessment including vital signs of temperature, heart rate, and blood pressure. Blood will be collected from a vein in the arm, or rarely a vein in the hand. A complete blood count, or CBC, will be done to ensure that blood levels are sufficient and that blood donation is safe for a patient to do. Patients need to have enough hemoglobin, the part of red blood cells that transports oxygen throughout the body. The blood will also be tested to confirm the type of red blood cell traits of patients. About 1 to 8 tablespoons may be collected, but most blood samples will be small, that is, 1 to 4 teaspoons. After the patients' first visit, sessions will take 5-20 minutes. Blood collection will total no more than 2 cups from a donor during any 6-week period. Although the frequency of blood donations is not known at this time, it is unlikely that a patient will be asked to donate blood more than four times a year. It may be important for patients to undergo a repeat CBC or tests for blood chemistry if results are needed for research. Risks associated with blood collection are considered minimal. They include discomfort, occasional bruising or bleeding at the puncture site, and faintness.