It is now well-known that the absence of attention can leave us "blind" to visual stimuli that are very obvious under normal viewing conditions (e.g. a person dressed as a gorilla; Simons & Chabris, 1999). However, the question of whether hearing can ever be susceptible to such effects remains open. Here, we present evidence that the absence of attention can leave people "deaf" to the presence of an "auditory gorilla" which is audible for 19s and clearly noticeable under full attention. These findings provide the first ever demonstration of sustained inattentional deafness. The effect is all the more surprising because it occurs within a lifelike, three-dimensional auditory scene in which the unnoticed stimulus moves through the middle of several other dynamic auditory stimuli. (Contains 1 figure and 2 tables.)