Purpose: To describe the prevalence and incidence of loss of visual field among patients with birdshot chorioretinopathy (BSCR) and to describe the effect of therapy on such field loss in these patients. Design: Retrospective cohort study. Method: setting: Single-center, academic practice. study population: Fifty-five patients with BSCR evaluated from January 1984 through July 2006. procedures: Demographic, clinical, and visual field data were collected retrospectively. outcome measures: Visual field loss is defined as an abnormal visual field score on Goldmann perimetry within six months of presentation and during follow-up; rate of visual field loss is defined as the number of degrees lost per year. Results: Forty-eight eyes of 24 patients had Goldmann visual fields performed within six months of presentation and of these eyes, 75% and 56% had abnormal field scores for the I-4 and IV-4 isopters, respectively. Of the 28 eyes of 14 patients that received immunosuppressive drug therapy during the follow-up period, the rate of visual field "loss" prior to treatment was 107 degrees/year (95% confidence interval [CI]: 65, 148 degrees/year) and 56 degrees/year (95% CI: 5, 109 degrees/year) for the I-4 and IV-4 isopters, respectively. The rate of "gain" after institution of immunosuppressive drug therapy was 53 degrees/year (95% CI: 10 degrees lost/year, 98 degrees gained/year) and 30 degrees/year (95% CI: 20 degrees lost/year, 81 degrees gained/year) for each isopter. Conclusions: Visual field loss was common among our patients with BSCR. Usage of immunosuppressive drug therapy may reverse some of the visual field loss while therapy is employed.