OBJECTIVE Retinopathy of prematurity (RoP) is a retinal vascular disease and a frequent cause of blindness in infants. Our objective was to measure the frequency of RoP in infants with extremely low birth weight (ELBW, < 1,000 g) at the National Institute of Perinatology, Neonatal Intensive Care Unit (NICU), weighing the association of RoP with several risk factors and their results, such as refractive errors and strabismus. METHODS We carried out two cross-sectional observations of our prospective study: one near birth, and the second, after a long-term follow-up. Funduscopic examination was performed while the infants were in the NICU to detect RoP. Infants with RoP were followed up by means of visual examinations during an average 8-year period and results were compared with those of infants with ELBW without RoP. RESULTS Of the 139 screened infants at the NICU, 24.4% were identified with RoP: 79% of these with grade I retinopathy; 18% with grade II, and one infant with grade III retinopathy. The zones involved were as follows: zone 1, 12%; zone 2, 79%, and zone 3, 9%. The following were associated with retinopathy: eclampsia (p = 0.003); gestational age (0.01); multiple gestation (0.03); days of stay at NICU (< 0.001); mechanical ventilation (0.001); hypoxia (0.01); oxygen therapy (< 0.001); apnea (0.005); acidosis (0.001), and hypercapnia (0.001). Retinopathy was self-limited in all children. We found no differences in frequency of refractive errors and strabismus between children with RoP and controls. CONCLUSIONS We observed a moderately high frequency of RoP in infants with ELBW in Mexico City and recommended early mandatory screening for early intervention.