AbstractWe report a case of clinically significant hemolytic disease of the newborn due to Kpballoimmunisation requiring obstetric intervention. This case and a review of the literature are in contrast to reviews of hemolytic disease of the newborn that either ascribe no significance to the Kpbantigen or suggest that it causes only rare or mild disease. Analysis of our Kpb‐negative donor pool suggests that prior transfusion greatly increases the chance of alloimmunisation. The role of frozen rare donor registry cells as a public resource is emphasise