1. Among 13,000 selected blood specimens studied in 1954, there were 1882 which contained atypical antibodies, mainly anti-D.
2. Of the 177 sera with atypical antibodies other than anti-D, 85 contained anti-c, anti-E or anti-K and 18 sera contained anti-Lea.
3. There were 52 cases of intragroup hemolytic disease, more than half of which were due to anti-c.
4. Intragroup isoimmunization with production of antibodies other than anti-D was detected in 47 cases as incompatibility in the crossmatching. In 31 additional cases failure to detect incompatibility resulted in transfusion reactions.
5. There were 30 examples of very rare Rh genotypes due to the presence of rare chromosomes dCe (r'), dcE (r''), DCE (Rz), and the rarest of all, dCE (Ry). All told, there were 7 bloods which contained chromosome dCE (ry) including one—the first of its kind—which was homozygous.
6. It is recommended that rare genotypes be registered on a world-wide basis under the auspices of a suitable agency and that these bloods be made available as test cells or as compatible donors.
7. Sixty-two cases of ABO hemolytic disease are reviewed briefly. In all but four the mothers were in group O. Of the 55 group O mothers tested, all but 5 showed enhancement of the specific antibody in the indirect Coombs reaction.