Haplo-insufficiency at the paired box gene 6 (PAX6) locus causes aniridia,which is characterized by iris hypoplasia and other anterior and posterior eye defects leading to poor vision. This study aimed to identify novel PAX6 mutations that lead to familial and sporadic aniridia in northeastern China.Two aniridia patients from a family and a sporadic patient underwent full ophthalmologic examinations. Genomic DNA was isolated from the affected individuals, 5 noncarriers in the family and 100 healthy normal controls. The coding regions and the adjacent intronic sequence of PAX6 were amplified by polymerase chain reaction (PCR) and direct bidirectional sequencing.A nonsense mutation in exon 9 (c.718C>T) was identified in the patients but not in any other unaffected families. A C>T substitution at codon 240 converts an arginine codon (CGA) to a termination codon (TGA).The same mutation was detected in the sporadic patient by chance.A mutation in the PAX6 gene was confirmed to be capable of causing the classic aniridia phenotype. This is the first report on the "hotspot" c.718C>T transition from northeastern Chinese families.