SummaryA family showing the Pelger‐Huët anomaly of the neutrophil polymorphonuclear leucocytes is described, the first to be reported in England. Thirty‐four affected individuals have been examined; thirty‐one of these and thirty‐eight unaffected people, either parents or sibs of affected members, have been grouped for theABO, MNS, Eh, P, Lewis, Kell, Lutheran and Duffy blood‐group systems. No linkage was demonstrated.We are indebted to Dr A. E. Mourant for most of the anti‐sera used in this investigation and to Drs D. Lehane and P. L. Mollison for supplies ofanti‐Fya. We are grateful to the members of the family described here for their co‐operation. We would like to thank Mr W. Rivers, Senior Technician, King's College Hospital, for preparing the pedigree chart and Mr W. Smith, Medical Photographer, King's College Hospital, for the