A cross-ideological group of ethicists recently signed a powerful public letter opposing the proposed federal regulation banning the sale of hematopoietic stem cells, used in bone marrow transplantation. These cells are used in the treatment of patients with serious blood or bone marrow cancer. Often, cell transplantation is needed to save the patient’s life. The new rule would reverse a 2011 court decision holding that offering payment to bone marrow donors is not forbidden by the National Organ Transplantation Act, if it is done by means of a new, relatively noninvasive procedure known as apheresis.