OBJECTIVE To determine the incidence of primary angle-closure glaucoma (PACG) and to assess the visual outcomes of patients treated for PACG. METHODS Population-based retrospective incidence study. METHODS Residents of Olmsted County, Minnesota, aged 40 years and older and diagnosed with PACG in the 13-year period between January 1, 1980, and December 31, 1992. METHODS Incident cases of PACG identified through the Medical Diagnostic Index of Mayo Clinic, Rochester, Minn, and the Rochester Epidemiology Project. RESULTS Thirty-six incident cases were identified. The mean annual age-and sex-adjusted incidence per 100000 people aged 40 years and older was 8.3 (95% confidence interval, 5.6-11.0). The probability of monocular blindness associated with PACG at the time of diagnosis was 14%. Among patients not monocularly blind at diagnosis, the 5-year probability of developing monocular blindness associated with PACG was 4%. CONCLUSIONS Primary angle-closure glaucoma is an uncommon disease in our community. Most of the patients blinded by PACG were blind at the time the condition was diagnosed.