PURPOSE: The RHO C110Y mutation has been recently reported to cause a phenotypically unspecified form of autosomal dominant retinitis pigmentosa (adRP). The study of a family affected with this mutation allowed us to hereby describe the genotype/phenotype correlation associated with the RHO C110Y mutation. METHODS: A six-generation pedigree cosegregating adRP and RHO C110Y in ten accessible individuals was ophthalmologically investigated. All family members affected with RP went through complete eye examination and ERG testing. RESULTS: The disease first manifested with nyctalopia during adulthood and slowly progressed over the next decades towards tubular visual field defects and relatively preserved central vision. Ophthalmoscopically, the fundus remained almost unaltered until the end of the third decade of life, and then slowly progressed towards typical RP changes with minimal macular involvement by the eighth decade. Color vision remained unaltered. Earliest ERG alteration was limited to the rod system followed by a rod-cone pattern. Scotopic and photopic ERG were recordable until the fourth and sixth decades, respectively. DISCUSSION: RHO C110Y-associated adRP is characterized by a late onset and a mild progression compatible with type 2 or regional RP with little intrafamilial phenotypic variability and complete penetrance. Characterization of genotype-phenotype correlations plays a role in the improvement of genetic and prognostic counselling.