There is little question that Frozen-Thawed-Deglycerolized Red Cells (Human) has the least amount of HLA antigen found in any red cell component. Units prepared by any of the several availables methods are indicated for patients with repetitive nonhemolytic febrile reactions, probably should be used in patients waiting for reanl allografts and in immunodeficient patients in whom there is a risk of GVH disease. Still unresolved are questions on the minimal dose of HLA needed to sensitize a recipient, the role of the debris and viable cells and whether transfusion with a small dose of HLA antigen has a beneficial effect on the survival of renal allografts.