Anti-LU8, an antibody defining a high-frequency antigen in the Lutheran system, was identified in the serum of a gravida 4 para 0 pregnant woman who had never been transfused. The antibody consisted of both an IgMandanlgGl component and was nonreactive in the antibody-dependent cell-mediated cytotoxicity (ADCC) assay. The red cells of the mother and 3 siblings of the patient typed as LU:8,14 and were incompatible with the patient’s serum. The baby was bom at term with a negative direct antiglobulin test and typed as LU:8,14. There was no clinical evidence of haemolytic disease of the newborn.