OBJECTIVE: To determine the potential impact of ultrasound-guided percutaneous pancreas allograft biopsy and standardized histologic grading on graft and patient survival in a solitary pancreas transplant program. DESIGN: Retrospective case series survey. SETTING: Tertiary care, university teaching hospital. PATIENTS: Thirty-five recipients of solitary pancreas transplants. INTERVENTIONS: Percutaneous pancreas allograft biopsies were performed in solitary pancreas transplant recipients. MAIN OUTCOME MEASURES: Actuarial graft and patient survival, cause of graft loss. RESULTS: Initiation of ultrasound-guided percutaneous pancreas allograft biopsy with standardized histologic grading is associated with a 70% 1-year graft survival and 93% 1-year patient survival in solitary pancreas transplantation. Acute rejection was responsible for only 11% of cases of graft loss. The presence of endotheliitis, vasculitis, or confluent acinar necrosis is associated with decreased pancreas allograft survival, poor response to corticosteroid therapy, and shortened time interval to ultimate graft loss. Clinical criteria for acute rejection such as elevated serum amylase or lipase levels, 50% decrease in urinary amylase levels, unexplained fever, or hyperglycemia are associated with a positive predictive value of only 72%. CONCLUSION: Pancreas allograft biopsy and standardized histologic grading are associated with significantly improved 1-year graft and patient survival in solitary pancreas transplantation.