The present article accesses the dependence of mismatch negativity of the human auditory event related potentials on the length of interstimulus interval. We employed passive oddball paradigm as a presentation method and simple tones were used as stimuli. This study was based on the assumption, that storage time of the memory trace, which is used for generation of mismatch negativity, is dependent on the length of the stimulus itself. As a result, the mismatch negativity was registered for short durations 11 ms stimuli. In such stimuli differences of amplitude of mismatch negativity depending on the length of interstimulus interval were also shown. Yet no such differences were found for stimuli of 20 ms and 30 ms. This result allows us to assume that storage time of memory trace of stimulus is directly proportional to the length of the stimulus itself when short interstimulus intervals are used. However, the increase of stimulus length over certain threshold does not show any changes in the properties of mismatch negativity.