Voluntariness stands for one of the four pillars of ethics in blood donation; it is, however, more related to tradition than to legislation. Because it seems necessary to apply "marketing" techniques to blood collection in order to meet the needs in blood components, both in terms of quantity and quality, one wonders if this may be at the expense of this principle of voluntariness. This seminar-belonging actually to a series of seminars in Ethics in Transfusion Medicine-aimed at questioning the possible weakness of voluntariness in the field of blood donation. To achieve this goal, specialists of numerous disciplines in medical sciences, law and humanities gathered to discuss all related issues to voluntariness in blood donation.