The aim of the present study was to evaluate whether treatment of subclinical, borderline rejections (SR/BR) or histological findings of chronic allograft nephropathy (CAN) in protocol biopsies in the first month posttransplantation after living related kidney transplantation has a beneficial effect on graft histology and renal function at 6 months. Among the 40 paired biopsies, only 6/80 showed no histological lesions. BR was found in 13/40 and 12/40, and SR in 15/40 and 21/40 of patients on the 1- and 6-month biopsies, respectively. The mean histological index/total sum of scores for acute and chronic changes (HI) increased at 6-month biopsy: 5.3 +/- 2.9 vs 7.8 +/- 3.6 (P < .001). Similarly, the mean sum of histological markers for chronicity (CAN score) of 2.1 +/- 1.5 increased to 4.6 +/- 2.3 (P < .001) on the 6-month biopsy. When divided according to whether there was treatment of BR and SR, the treated BR/SR group on 1-month biopsy had a mean HI score of 7.11 +/- 1.9, which remained almost the same (7.11 +/- 2.32) at 6 months. Among the untreated BR/SR group it increased from 4.95 +/- 1.99 to 8.16 +/- 4.30. However, there was no difference in graft function between the groups from 1 to 6 months. In conclusion, a protocol 1-month biopsy may be valuable to establish the prevalence of BR/SR in stable allografts. The presence of an untreated BR/SR upon a 1-month biopsy showed greater susceptibility for histological deterioration on the 6-month biopsy due to an accelerated CAN process.