PURPOSE: To estimate the mean rates of decline of ocular function in patients with an atypical form of retinitis pigmentosa, termed "pericentral retinitis pigmentosa." DESIGN: Retrospective observational study. METHODS: setting: Single-center. patient population: Eighteen patients (ages 32 to 65 years) with pericentral retinitis pigmentosa followed for 3 to 26 years. observational procedures: Snellen visual acuity, Goldmann visual field area (V-4e white test light), and full-field electroretinogram (ERG) amplitudes (0.5 Hz and 30 Hz white flashes). main outcome measures: Mean annual exponential rates of change quantified by repeated-measures longitudinal regression. RESULTS: Estimated mean annual rates of decline of remaining ocular function were 1.2% for visual acuity, 1.9% for visual field area, 2.5% for ERG amplitude to 0.5 Hz flashes, and 2.9% for ERG amplitude to 30 Hz flashes. CONCLUSIONS: The mean rates of loss of remaining ocular function of patients with pericentral retinitis pigmentosa were generally slower than those previously reported for patients with typical forms of retinitis pigmentosa.