An antibody has been found which identifies a "new" and rare antigen belonging to the MNSs system; it was found in the serum of Mrs. Verd. before the birth of her last child. Mr. Yerd. has the antigen and so has the child; at birth the child’s cells gave a weak positive direct anti-globulin reaction, in part, or perhaps wholly, due to weak anti-D which became detectable in the mother’s serum during the puerperium. The child was healthy. For the present we are calling the antigen Vr : much more knowledge about the antigens Hu, He, Mi^a, Vw and Vr will be needed before attempts to tidy up the MNSs notation can usefully be made.