Pelger-Huët anomaly is an inherited abnormality of neutrophils, characterized by reduced nuclear segmentation and an apparently looser chromatin structure. Following linkage studies in two families, the lamin B-receptor (LBR) was sequenced and mutations found: CCG-->CTG causing proline-->leucine in codon 119 of exon 3, and IVS11-9 A-->G, disrupting the splice acceptor site. The LBR gene (LBR) was also sequenced from a single English man with Pelger-Huët anomaly and a heterozygous C-->G mutation was found in codon 569 of exon 14, predicted to cause a proline-->arginine. Our results confirm recently published findings that LBR mutations cause Pelger-Huët.