PURPOSE: This hospital-based study was carried out to assess the common causes of blindness in Ibadan, the largest city in the southwestern part of Nigeria, and to strengthen the primary eye care approach to control and reduction of cases of blindness in the community. METHODS: Following Hospital Ethical Board approval and informed consent of participants, a prospective study was performed in which 1,544 consecutive patients with bilateral or unilateral blindness seen between January and December 2003 at the Ring Road State Hospital, Ibadan, Nigeria, were evaluated for causes of blindness. Visual acuity was measured with an illuminated Snellen chart placed 6 meters away from the participants. This was followed by pen torch examination and dilated funduscopy with a direct ophthalmoscope. Friedman field analyzer was used to measure visual field. Patients with corrected visual acuity of less than 3/60 in the better eye or with visual field of less than 10 degrees from fixation were considered blind according to the World Health Organization criteria. RESULTS: The 1,544 patients had a mean age of 53.5 years (range, 4 to 96 years); 858 (56%) were male and 686 (44%) were female. Blindness was bilateral in 471 (30%) patients and unilateral in 1,073 (70%). When those persons with unilateral and bilateral blindness were grouped together, individuals within the 60 to 79 years age bracket were 667 (44%) and constituted the largest group of all blind persons. The leading causes of bilateral blindness were cataract, 171 (36%); glaucoma, 138 (29%); and optic atrophy, 21 (4%). The most common causes of unilateral blindness were cataract, 446 (41%); glaucoma, 213 (20%); and those referable to trauma, 116 (11%). CONCLUSIONS: Cataract and glaucoma are the main causes of bilateral and uniocular blindness in the study area.