Tubulitis is the principal lesion used for the diagnosis of acute rejection (AR) in the Banff schema for renal allograft pathology. It is considered to be reliable for assessing AR early after transplantation. However, its significance in biopsies with concurrent changes of chronic allograft nephropathy (CAN) is less well understood. To address this issue we studied seventeen allograft biopsies taken 9-108 (median 39) months post-transplant from 17 patients. All specimens were scored for AR and CAN using Banff criteria. Medical records were reviewed to determine the clinical course of the patients. Five biopsies showed t1 changes, whereas nine biopsies graded as t2, and three biopsies as t3. The CAN scores varied from cg0, ci1, ct1, cv1, to cg1, ci3, ct3, cv3. A response to increased immunosuppression, defined as a fall in the serum creatinine of at least 20% compared to the peak value, was observed in 7/17 (41%) cases. The responsive cases included 2/5, 4/9, and 1/3 cases respectively with t1, t2, and t3 tubulitis. The mean +/- SD CAN scores in these three groups were 8.4 +/- 1.8, 6.5 +/- 1.4, and 7.0 +/- 1.4, respectively. We conclude that the presence of coexisting tubulitis and CAN in renal allograft biopsies may indicate reversible acute rejection. In this study, clinical response was observed in 7/17 (41%) patients. Patients with therapeutically responsive rejection could not be differentiated from refractory cases by serum creatinine, tubulitis grade, per cent glomerulosclerosis and sum scores for AR or CAN. Hence a trial of anti-rejection therapy may be warranted pre-emptively in all such cases.