This paper describes three experiments which demonstrated the presence of binaural perception abilities (the ability to use both ears) in 4-month-old but not in 2-month-old infants. All of the experiments employed a visual fixation habituation-dishabituation paradigm in which infants were given a series of visual fixation trials while binaural stimuli were presented through earphones. The first experiment tested the perception of interaural time differences. There was a significant increase in looking time on the first dishabituation trial for the 4-month-old infants. The second experiment tested the perception of interaural intensity differences. When the tones to the two ears were exchanged on the dishabituation trials, there was again a significant increase in fixation time for the 4-month-olds. The third experiment tested for binaural release from masking. Identical noise was presented to each ear during trials 1-7. A low intensity in-phase tone was added during trials 6 and 7. The same tone was presented out of phase on trials 8-10. The 4-month-olds showed no change in fixation during trials 6 and 7, but showed a significant increase on trial 8. The results of the experiments indicate that infants as young as 4 months of age are able to utilize binaural information in much the same way as adults. (Author/BD)