Five infants and children with a history of mild retinopathy of prematurity (ROP) were tested for postulated alterations in rod photoreceptor function. The photoreceptor responses were derived from the electroretinographic alpha waves. Postreceptoral components, the beta wave and the oscillatory potentials, were also examined. The saturated amplitude and sensitivity of the rod photoreceptor responses were low, except for the sensitivity in one patient. The beta-wave sensitivity was low, but saturated amplitudes were within the 95% prediction interval for normal. The amplitudes of the oscillatory-potential responses were also attenuated. The results indicate that retinal dysfunction may be present in patients with a history of mild ROP long after the ROP has completely resolved. Additionally, the data suggest that the photoreceptors are the primary site of retinal dysfunction in mild ROP.