The incidence and nature of binaural responses were determined for 174 units in the inferior colliculus of 16 anaesthetized kittens aged between 5 and 35 days. As early as the first week of life a majority of units is influenced by binaural stimuli, and in this and subsequent weeks of life the forms of binaural interaction characteristics of the adult may be recognized. Best frequencies for given units excited by stimuli applied to either ear were very similar. The results indicate that binaural connections may be established at or before the onset of hearing in the cat.