European regulations for blood donation recommend a maximum donor age of 65 years. On the other hand, the percentage of the population in this age group is rapidly increasing in Western countries, and in autologous blood donation programs this limitation has already been abandoned. In a prospective study we examined blood donation in elderly donors (18 male and 5 female; mean age 65 years, range 64-69) in comparison to a younger control group (15/9; 58, 55-63). All donors were regular blood donors and had donated for at least 3 years. We investigated the exercise capacity before and after donation of 450 ml whole blood by examination of the physical working capacity (PWC) at heart rates of 110/min and 130/min through treadmill exercise testing and determined the blood viscosity. Additionally, whole-blood count, hemoglobin, plasma-ferritin levels and total iron binding capacity were measured immediately after donation and on days 7, 28 and 49. We found a decrease in whole-blood viscosity and a moderate increase in PWC at heart rates of 110/min and 130/min after donation in both groups. Red cell count and values of hemoglobin and ferritin were significantly lower in both groups after donation and returned to pre-donation values by day 49 in the younger control group. We detected no deterioration in exercise capacity after whole-blood donation in elderly blood donors over 65 years when compared with a younger control group. We suggest that blood donation in otherwise healthy persons aged over 65 years should be accepted.