55 renal allograft biopsies obtained during acute rejection episodes resistant to standard antirejection therapy in 36 renal transplant recipients were reviewed and the findings correlated with long-term graft prognosis. 20 patients demonstrated moderate vascular pathology (group A), while 16 patients demonstrated changes consistent with pure cell-mediated rejection with no vascular lesions (group B). Groups were similar with respect to age range, duration of haemodialysis, sex and antigen match. Of patients with vascular changes, 11 had arterial changes, 9 had arteriolar changes and 6 had arterial and arteriolar changes. The cumulative graft survival for group A was significantly less than that for group B at all post-transplantation intervals up to 24 months (p < 0.001).