PURPOSE To evaluate the long-term outcome of primary congenital glaucoma in patients followed for more than 20 years. METHODS All patients with a diagnosis of congenital glaucoma who were examined in the pediatric glaucoma clinic at Moorfields Eye Hospital from 2005 to 2006 were included. The follow-up period was a minimum of 20 years; patients with pediatric glaucoma secondary to other etiologies were excluded. Data collected included visual acuity, optic disk cupping, intraocular pressure (TOP), corneal diameter, pachymetry, visual fields, refraction, strabismus, glaucoma management, and ocular comorbidity. Progressive congenital glaucoma, defined as an increase of the cup/disk ratio of >0.2 secondary to elevated TOP, was evaluated with the use of Kaplan-Meier survival curves. Patients were divided into 1 of 3 groups: (1) stable glaucoma with no visual impairment; (2) glaucoma progression with sight-threatening consequences; and (3) poor visual acuity as a result of ocular comorbidity. RESULTS A total of 30 eyes of 16 patients were identified. Mean follow-up was 34 +/- 10 years (range, 22-59 years). At the final clinical assessment, mean IOP was 13.6 +/- 4.3 mm Hg and mean cup/disk ratio was 0.7 +/- 0.3 (p < 0.05). Survival analysis demonstrated lack of progression in 90.3% at 1 year, 83.1% at 5 years, 70.8% at 10 years, 58.3% at 34 years, and 48.6% at 40 years. CONCLUSIONS Apparently stable congenital glaucoma may progress with sight-threatening complications after many years of TOP stability. Monitoring of these patients is indicated throughout life. (J AAPOS 2011;15:148-152)