To identify TIGR gene mutation in two Korean pedigrees of primary open-angle glaucoma (POAG), and in 25 steroid-induced glaucoma patients, TIGR gene assay was performed. Genomic DNA was extracted from peripheral blood and the TIGR gene was amplified by polymerase chain reaction (PCR). The PCR amplification products were evaluated by single-stranded conformation polymorphism and direct DNA sequencing. In POAG families, not only those patients clinically diagnosed as glaucoma, but also most of their siblings, in whom glaucoma had not yet been detected, had a proline-to-serine (TCC-to-CCC) mutation in codon 334. However, no steroid-induced glaucoma patients showed TIGR gene mutation. TIGR gene mutation, in familial POAG, was found in a different codon from that previously reported. The TIGR gene does not, however, seem to be related to steroid-induced glaucoma.