Histological evidence of retinal damage associated with the clinical observation of Retinopathy of Prematurity (ROP) grade III was documented in preterm infants receiving the minimum dosage of vitamin E recommended by the American Academy of Pediatrics (5 mg/kg/day), and exposed to high concentration/duration of oxygen at birth. Matched infants that were provided a higher oral dosage of vitamin E (100 mg/kg/day) did not develop the serious grade of retinopathy (grade III) (1,2). In this paper cytological correlates are described which substantiate pre-existing theories concerning the pathological changes associated with the development of the disease at a light microscopic level. Moreover, observations made at the elec tronmicroscopic level permit distinctions to be made concerning the newly formed retinal vessels, in treated versus non-treated infants, that have not been noted in the history of this disease. These retinal distinctions suggest that vitamin E may be efficacious in reducing the severity of ROP. Lastly, a mechanism is suggested for the action of vitamin E in reducing the severity of ROP.