THE success of solid organ transplantation has been dependent on the ability to distinguish rejection from non-immunologic causes for graft dysfunction through the examination of tissue samples. Pancreas allograft biopsies are now obtained routinely percutaneously and constitute a significant guide for treatment and prognosis. We have previously proposed a scheme for grading pancreas allograft rejection in needle biopsies that is predictive of the graft outcome. This scheme is based in the proportionally increasing inflammation in specific tissue components. In this study, we evaluated the reproducibility of the grading system and the potential diagnostic problems between the various grades of rejection and other nonimmune related processes.