Anti-M^e is an antibody which cross-reacts with the M and He antigens. It has previously only been found in rabbit serum; the first human example is described. The Henshaw antigen is closely associated with the MNSs system and is found in about 3% of Negroes [1-3] but only rarely in Caucasoids , The original anti-He was found in a rabbit anti-M serum by Ikin and Mourant  in 1951. Other examples were deliberately produced by the immunisation of rabbits with the blood of Mr. Henshaw . The first example of anti-He in a human serum was found in 1967 by MacDonald et al.  in a Caucasoid mother. Although at the time it was not possible to ascertain the racial group of the father, it has since been established that he was a Negro. Other human anti-He sera have since been found . In 1961 Wiener and Rosenfield  reported an immune rabbit serum which possessed inseparable anti-M and anti-He specificities which they designated anti-M^e. The rabbit which produced the anti-Me had almost certainly not received Henshaw-positive cells. The rabbit serum was investigated as a result of a discrepancy found during M-typing of a Negro involved in a medicolegal case of disputed parentage. The first human example of anti-M^e herein described was found in the serum of Mr. Richards, a 41-year-old Caucasoid male with no known transfusion history and has been used at this centre as an anti-M serum for many years.