Transplantation is recognized as one of the greatest triumphs of modern medical science, but we are confronting the severe shortage of organs for transplantation. Xenotransplantation, the transplantation of nonhuman organs, tissues or cells into humans could be an alternative to fundamentally resolve this problem. Despite the potential benefit, xenotransplantation also gives us a potential risk, which are rejection and infection. The potential immunological rejection means the possibility of the human immune system to reject any foreign object. The rejection mechanism is very similar to that by which the body resists infection. The rejection of foreign object may endanger the life of the recipient. In xenotransplantation, immunosuppressive drugs can be clinically used to prevent the rejection of foreign object. However, these toxic drugs have side effects: the immune system loses its ability to successfully resist infections. The potential risk of infection means xenozoonosis that might result from xenotransplantation. For example, a pig virus, especially PERV might infect the human recipient, mutate and spread first to the close contacts of the recipient and then to the general population. This article primarily focuses on warning the risk of rejection and infection. This article also discusses clinicaltrials, informed consent and legal liability as legal aspects of xenotransplantation. Especially, an in-depth study is further required on legal implications and toxicology of xenotransplantation because the use of immunosuppressants for resolving immune rejection may bring lots of potential toxicologic problems. While clinical trials and informed consent are pretransplant prevention against the potential risk as preconditions for xenotransplantation, legal liability is posttransplant protection from it.