Infant looking time was monitored during habituation to the repeated presentation of a wavelength stimulus selected from one basic adult hue category and after a change in stimulation. Recovery from habituation was greater to a wavelength selected from an adjacent hue category than to a wavelength from the same category even though these two stimuli were equally distant (in nanometers) from the habituation wavelength. Differential responding evidenced infants' categorical perception of hue; that is, infants see the physically continuous spectrum as divided into the hue categories of blue, green, yellow, and red. These results help to resolve the long-standing controversy surrounding the primacy of perception over language in the organization of hue.