The aim of the study was to evaluate the evolution of glomerular volume 4 months after transplantation. Mean glomerular volume (Vg) was estimated according to the Weibel and Gomez method in a donor and a protocol biopsy done at 139 +/- 58 d in 41 stable grafts. Biopsies were also evaluated according to the Banff schema. Vg increased after transplantation from 4.1 +/- 1.4 to 5.1 +/- 2.4 x 10(6) micro3 (p=0.02). In patients with chronic allograft nephropathy in the protocol biopsy (n=14), the Vg enlargement was -0.3 +/-x 10(6) micro3 while in patients without chronic allograft nephropathy (n=27), glomerular enlargement was 1.6 +/- 2.1 x 10(6) micro3 (p=0.01). There was a negative association between glomerular volume in the donor biopsy and glomerular enlargement after transplantation (R=- 0.34, p=0.03). Multivariate regression analysis confirmed that Vg in the donor biopsy and chronic allograft nephropathy in the protocol biopsy were independent predictors of glomerular enlargement after transplantation (R=0.48, p=0.01). Moreover, Vg in the protocol biopsy correlated with creatinine clearance at the time of biopsy (R=0.38, p=0.01). Glomeruli enlarge after transplantation and glomerular volume after 4 months correlates with creatinine clearance, suggesting that glomerular enlargement is a necessary condition for renal adaptation to the recipient. Glomerular enlargement is impaired in patients with chronic allograft nephropathy.