PURPOSE To identify the genetic mutation associated with distinct cases of open-angle glaucoma noted in a Chinese family. METHODS Clinical examination and pedigree analysis were undertaken in a family with a large number of primary open-angle glaucoma cases. Venous blood samples were drawn from six affected and six unaffected subjects in the family. Genomic DNA was extracted. Linkage to the optineurin gene (OPTN) locus was not excluded. Potential mutation in OPTN was screened by polymerase chain reaction (PCR) analysis of its exon regions and direct sequencing. RESULTS A missense mutation, A1274G, in exon 10 of OPTN was identified in affected patients of the family. The corresponding amino acid change was Lys322Glu. This mutation was not found in unaffected family members of the family or in 87 unrelated normal controls. CONCLUSIONS A novel mutation of a Lys322Glu change in OPTN is responsible for this familial case of primary open-angle glaucoma observed in northeastern China.