With the hope that the electroretinogram (ERG) in preterm infants could help clarify their vitamin A requirements, a technique for recording the full-field ERG in the neonate is described. One hundred seventy-seven ERGs were performed in 59 preterm and 52 term infants. An ERG was recorded as soon as 7 hours after birth and as early as 30 weeks after conception. In preterm infants the a-wave latency was longer and the amplitude less than in term infants of the same age. The amplitude of the ERG in preterm infants increased with the duration of light exposure. Longitudinal data on 15 preterm infants showed a reduction in a-wave latency. None of the ERG findings correlated with postconceptional age, which suggests that the duration of light exposure is a major determinant of the ERG pattern in preterm infants. Despite low circulating levels of retinol, no correlations with any of the ERG values were found.