The importance of the donor/recipient body weight ratio (DRBWR) as a cause of kidney graft loss was evaluated in 112 non-diabetic, ciclosporin-treated, first cadaver kidney transplant recipients. According to the DRBWR, the patients were divided into three groups: 'low' (< or = 0.80), 'medium' (0.81-1.20), and 'high' (> 1.20). The three groups did not differ in patient or graft survival, and the DRBWR was not a predictor of graft failure at multivariate analysis (Cox models), even after only patients with graft survivals > 1 year were considered. The three groups did not differ in glomerular filtration rate (GFR) and proteinuria 6-60 months after renal transplantation. When the 55 patients with a follow-up period > 4 years were considered, no differences between groups were found in GFR or GFR evolution over time. Hypertension was significantly less frequent in group 'high' (Mantel-Cox p = 0.04), but very likely as a consequence of uneven recipient gender (an independent predictor of hypertension at multivariate analysis) distribution between groups, the significance being lost when survival curves were rebuilt by stratifying for recipient gender. DRBWR never resulted as a significant predictor of GFR at multivariate analysis when GFR values 6-60 months after transplantation were analyzed. We conclude that the DRBWR has no major effects on kidney graft function and survival in the short to medium term.