The use of short-term memory under audio-visual presentation was investigated. The experiment consisted of two tests. An identification test was carried out to provide a baseline for the influence of visual information on auditory judgment. An AX-discrimination test was conducted to examine the role of short-term memory of audio-visual stimuli. It was observed that (1) the timbre of the fused percept was judged to be modified by visual information, (2) stimulus order effects occurred under audio-visual presentation, (3) the inter-stimulus interval influenced the discrimination of audio-visual stimuli. The results suggest that two kinds of short-term memories are involved in the discrimination of audio-visual stimuli and that the auditory memory of the fused percept is influenced and modified by visual information.