After evaluation by a team of transplant professionals, a patient is added to the national waiting list by the transplant center. Lists are specific to both geographic area and organ type: kidney, pancreas, kidney-pancreas, liver, intestine, heart, lung, and heart-lung. Each time a donor organ becomes available, a computer generates a list of potential recipients based on factors that may include genetic similarity, organ size, medical urgency, and time on the waiting list. Through this process, a new list that best matches a waiting patient to a donated organ is generated each time an organ becomes available.