The effects of early monocular form deprivation on the developing mammalian visual system, and the anatomical and physiological consequences of early monocular enucleation, suggest that the remaining eye of human subjects who had the other eye removed early during development might be capable of supernormal performance. To test this inference, the achromatic contrast sensitivity of the remaining eye of subjects who had the other eye removed at different ages after birth was compared with that of normal subjects tested under monocular and binocular conditions. The results show that all subjects who had an eye removed during early development had a higher contrast sensitivity than the better eye of control subjects. Furthermore, the earlier in development that the eye was removed, the lower the spatial frequency at which contrast sensitivity is enhanced compared with measurements made in the better eye of control subjects, and the larger the range of spatial frequencies over which contrast sensitivity is supernormal.