The invention relates to a method and an immunological test kit for predicting the risk of transplant rejection by detecting anti-AT1 receptor auto-antibodies in biological materials of a patient to be examined, e.g. by an immune reaction with the AT1 receptor or functionally analogous peptides or proteins thereof. The invention is also directed to the use of the AT1 receptor or functionally analogous peptides or proteins in order to predict (diagnose) the risk of transplant rejection. Said risk exists if anti-AT1 receptor auto-antibodies can be detected in such biological materials, e.g. in body fluids or tissues.