Abstract.The published specifications of the acceptable limits of the maximum plasma volume to be ‘harvested’ by plasmapheresis from one individual per year vary from 10–15 liters in Europe to 50–60 liters in the United States. To answer the question which of these widely diverging precepts is appropriate, the effects of plasmapheresis on serum protein levels and their relationship to albumin metabolism, the accepted safeguards for the donation of whole blood, and the disease known as the nephrotic syndrome are considered. A living person who consents to his bodily integrity being violated for the benefit of others must be protected not only against the generation of manifest illness by such violation, but also against any prolonged deviation from the normal state of his body. It is concluded that plasmapheresis donors should not deliver more than 10 to 15 liters of plasma per year, as now recommended by European authorities. Not more than 500 ml of plasma should be withdrawn per session, and the interval between two such sessions should not be less than