The serious shortage of brain-dead donors leads to the use of pancreata from marginal donors, including cardiac death in Japan. We studied the islet histology of pancreas graft biopsies to investigate the adequacy of using pancreata from marginal donors. Pancreas allograft biopsy was performed originally to diagnose acute rejection (Drachenberg grade I-III) at a mean of 6 months after transplantation. The percentage of beta cells showing oxidative DNA changes, replication, and apoptosis was investigated in 7 recipients of simultaneous pancreas-kidney transplantations with good graft function from marginal donors. Their causes of death were cerebrovascular with donor ages >44 years (n = 3), cardiac (n = 2), and cerebrovascular (n = 2). The percentage of beta cells per islet in the transplanted pancreas (71.9 +/- 3.3%) did not correlate with glycemic control or insulin secretion, but did correlated inversely with donor age (r = -0.81; P < .05). Oxidative DNA changes as revealed by 8-hydroxy-2'-deoxyguanosine (8-OHdG) staining were diffusely present in islet cells as well as in the exocrine cells of the transplanted pancreas. The percentage of 8-OHdG-positive cells per pancreas (71.8 +/- 4.5%) did not correlate with glycemic levels, insulin secretion, donor age, or ischemic time. There were no Ki67-positive replicating cells or terminal deoxynucleotide transferase-mediated dUTP nick-end labeling-positive apoptotic islet cells. Transplanted pancreata from marginal donors showed preserved beta cells and function despite diffuse oxidative changes.