Renal function impairment is common after solid organ transplantation, due to the nephrotoxicity of cyclosporine. Moreover, in patients with severe respiratory failure, renal function is often impaired. This renal function impairment may predispose patients to further renal function impairment after lung transplantation. Therefore, renal hemodynamics were measured in 44 patients before lung transplantation and 1, 6, 12, 18, 24, and 30 months after transplantation. After transplantation, a decline in renal function occurred, with a progressive fall in glomerular filtration rate (GFR) of 33 +/- 4% at 12 months and 42 +/- 9% at 30 months. Effective renal blood flow fell by 22 +/- 5% at 12 months and remained stable thereafter. Changes in effective renal plasma flow (ERPF) were less pronounced than those of effective renal blood flow, due to a fall in hematocrit after transplantation. Blood pressure and renal vascular resistance increased significantly, consistent with the effects of cyclosporine. Prior to transplantation, renal function impairment with intense renal vasoconstriction had been found in a subset of the patients. Remarkably, the decrease in renal function after transplantation was less pronounced in patients with renal function impairment prior to transplantation, as indicated by significant negative correlations between pretransplantation GFR and the percentage change in GFR after transplantation, and pretransplantation ERPF and the percentage change in ERPF after transplantation. This suggests that the net course of renal hemodynamics after lung transplantation is the result of the opposed effects of cyclosporine nephrotoxicity and the favorable effects of the normalization of respiratory status. In conclusion, after lung transplantation a decline in renal function occurs that is less pronounced in patients with renal function impairment and intense renal vasoconstriction prior to transplantation. Such a renal function impairment, therefore, should not be considered a contraindication to lung transplantation.