BACKGROUND: Increasing numbers of living donor kidney transplantations calls for better knowledge about long-term donor outcomes and risks. METHODS: To explore long-term kidney donor outcomes and risks, we conducted a cross sectional retrospective study. To this end, we analysed renal function using measured glomerular filtration rate (mGFR) and estimated glomerular filtration rate (eGFR) as well as microalbuminuria, blood pressure (BP), body mass index, haemoglobin, albumin and parathyroid hormone in kidney donors nephrectomized between 1965 and 2005. RESULTS: A total number of 573 kidney donors agreed to undergo medical follow-up examinations. The mean age (standard deviation) at donation was 47 (11) years and the mean time since donation was 14 (9) years. Both mean mGFR [68 (15) mL/min/1.73m(2) body surface; P = 0.028] and mean eGFR [71 (16) mL/min/1.73m(2) body surface; P 140/90 mm Hg). CONCLUSION: Renal function of the remaining kidney in living donors is expected to improve for many years but will show signs of slight deterioration in the longer run.