Background: Since the first kidney transplantation took place in Boston in 1954, vast progress has been made regarding prevention, diagnosis and treatment of rejection as well as understanding underlying mechanisms. As a consequence immunosuppressive therapy has become more tailored and the results have improved considerably. Since 1991 the Banff group has arranged meetings every other year, to evaluate issues related to renal allograft pathology and in particular, to establish robust diagnostic criteria for classification of different types of rejection. Over the years the Banff classification has developed, to become the major standard setting in the international field of transplantation pathology. The aim of the presentation is to give a general overview of kidney transplantation in Norway, the different rejection mechanisms and the Banff criteria for diagnosing rejection in a kidney biopsy. Method: The presentation is based on articles found by systematic search in UpToDate and PubMed, and by using relevant articles found in the references, as well as using medical textbooks.