Recent electrophysiological and anatomical experiments in rats and cats have shown that treatment with the neurotrophic factor — nerve growth factor (NGF) — prevents the effects of monocular deprivation (MD) at the level of visual cortex and lateral geniculate nucleus. We tested whether NGF treatment was effective in preventing MD effects on visual behavior of monocularly deprived kittens. Behavioral visual acuity was measured in kittens that had been monocularly deprived and treated intraventricularly with NGF for 2 weeks during the critical postnatal period. The detrimental effects of MD on behavioral visual acuity were found to be largely prevented by NGF treatment.