Familial neurohypophyseal diabetes insipidus (FNDI) is a disorder characterized by excess excretion of diluted urine (polyuria) and increased uptake of fluids (polydipsia). The disorder is caused by mutations affecting the AVP-NPII gene, resulting in absent or deficient secretion of the antidiuretic hormone arginine vasopressin (AVP) by the neurohypophysis. In this study we examined a three-generation Cypriot kindred suspected to have FNDI. Direct sequencing analysis of AVP-NPII identified a missense mutation (NM_000490.4:c.61T>C; p.Tyr21His; rs121964893) within the AVP moiety on exon 1 of the gene in all affected family members. So far, only three studies have reported mutations within the AVP moiety of AVP-NPIIas being associated with FNDI, with the vast majority of identified FNDI mutations being located within the signalling peptide or the neurophysis II (NPII) moiety of the gene. The mutation within the AVP moiety identified here had been reported previously in a Turkish kindred with FNDI. Consequently, the findings of this study confirm the causal role of mutations within the AVP moiety in FNDI. Herein we review reported mutations within the AVP moiety of AVP-NPII and their contribution to FNDI.