Binocular visual field development was measured in 11 infants who had stage 3 ROP in early infancy and in 11 infants without ROP, matched for birthweight and gestational age. Kinetic perimetry was used to measure visual fields along the 45 degree, 135 degree, 225 degree and 315 degree half-meridia. Infants were tested at 4, 9, and 18 months from due date. Analyses of variance were used to compare results of the two groups for each age tested. Results at the 4-month test age indicated that both groups had visual fields within the normal range for their age. However, at the 9-month test age the ROP group showed a significantly (P less than 0.05) smaller visual field than the control group. At 18 months, the ROP group still showed smaller visual fields than the control group, but the difference was not significant. The results suggest that dysfunction of the peripheral retina associated with ROP may produce a constriction of the visual field or a delay in visual field development.