PURPOSE OF REVIEW: Histological abnormalities are commonly present in late posttransplant biopsies. Many of these changes are seen in recipients who are clinically well with good graft function. This review includes discussion of a small number of studies published within the past 18 months and details future directions in this area of research. RECENT FINDINGS: An analysis of protocol liver biopsies in adult liver allograft recipients revealed normal or near normal histology in less than one third of recipients. Idiopathic chronic hepatitis (not related to disease recurrence) was present in 33%. Interpreted in light of the calculated creatinine clearance, the histological findings led to a documented change in immunosuppression in 32% of the recipients studied. Another study that assessed the natural history of graft fibrosis after pediatric liver transplantation revealed that fibrosis was strongly related to transplant-related factors, and that by 10 years following liver transplantation, the severity had progressed in 25% of the studied recipients. SUMMARY: Current studies suggest protocol liver biopsies may provide important histological information about graft function that is not available from standard liver tests and may allow modification of immunosuppression to ensure long-term side-effects of drug therapy are minimized while graft function is maintained.