To screen possible disease-causing mutations in the GUCA1B gene, GNGT1 gene,and the alternative-splicing region of RGS9 gene in 120 probands with retinitis pigmentosa,genomic DNA was collected from 120 probands with retinitis pigmentosa out of 120 families. The coding sequences of the GUCA1B and GNGT1 genes and the alternative splicing region of the RGS9 gene were analyzed by using PCR-heteroduplex-SSCP method. Mutation was confirmed by DNA sequencing. A T/C polymorphism was identified in exon 1 of the GUCA1B gene in 31 of the 120 probands. Heteroduplex-SSCP analysis of the GUCA1B and GNGT1 coding regions and RGS9 alternative splicing region showed no mutations in 120 patients with retinitis pigmentosa. We found no evidence that mutation in GUCA1B,GNGT1,or RGS9 gene is a cause of retinitis pigmentosa.