Monocular grating acuities of healthy preterm infants born at 27-36 weeks gestation were compared with those of fullterm infants age-matched on the basis of postnatal or adjusted (postconceptual) age. Matching on the basis of adjusted age resulted in closer agreement between preterm infant and fullterm infant grating acuity during the first year of life. Neither the age at testing nor the gestational age at birth influenced the better agreement found when the infants were matched on the basis of adjusted age. These results suggest that early exposure of the preterm visual system to visual stimulation does not lead to precocious visual development. In addition, the data provide norms for monocular grating acuity of healthy preterm infants and support the use of existing monocular normative data from fullterm infants for the evaluation of visually impaired preterm infants age-matched by adjusted age.