An attempt to determine the clinical significance of anti-Bga was performed by transfusing 51Cr-labelled red blood cells (RBC) from HLA-B7 positive donors to four patients who had histories of anti-Bga. Pre-and post-transfusion samples showed no change in antibody titer scores, haptoglobin or complement levels. Three of the patients were then transfused with 51Cr-labelled RBC from HLA-B7 negative donors and the half-life (T50Cr) of both were compared. Although low, the T50Cr of HLA-B7 incompatible RBC appeared to be similar to the T50Cr of HLA-B7 compatible RBC.