The rapid advances of the new immunology are beginning to be applied to the classic problems of immunohematology. Red cell alloimmunization is an important problem in transfusion and pregnancy, and several recent lines of evidence suggest links between red cell antibodies and autoimmunity. Pathogenic red cell autoantibodies are being studied for their fine specificity and structure. Modulation of red cell antibody responses may become feasible by using immunosuppression, anti-idiotypic antibodies, or interleukin blockage. Various clinical cofactors may affect the likelihood of immune hemolysis. Finally, new antibody technologies are being developed that may prove useful in blood banking.