The receptive fields of visual cortical neurons are bidirectionally modified by sensory deprivation and experience, but the synaptic basis for these changes is unknown. Here we demonstrate bidirectional, experience-dependent regulation of the composition and function of synaptic NMDA receptors (NMDARs) in visual cortex layer 2/3 pyramidal cells of young rats. Visual experience decreases the proportion of NR2B-only receptors, shortens the duration of NMDAR-mediated synaptic currents, and reduces summation of synaptic NMDAR currents during bursts of high-frequency stimulation. Visual deprivation exerts an opposite effect. Although the effects of experience and deprivation are reversible, the rates of synaptic modification vary. Experience can induce a detectable change in synaptic transmission within hours, while deprivation-induced changes take days. We suggest that experience-dependent changes in NMDAR composition and function regulate the development of receptive field organization in visual cortex.