Previous investigations have shown that for monaural presentations, identification accuracy of simultaneous vowels improves when a precursor with the same F[inf 0] and spectrum envelope is present which draws attention to a particular voice. In normal listening situations, however, one likely makes use of both ears rather than one ear only. The present investigation examined the ability of a dichotic precursor to enhance simultaneous vowel sounds presented to the left ear. A precursor was presented to the listeners whose intensity level in the left ear was the same as that used in previous investigations. However, the intensity of the precursor in the right ear was varied to produce different perceptual locations of the precursor: left ear only, 45(degrees) left of midline, midline, 45(degrees) right of midline, and right ear only. Thus the same monaural stimulus that has been shown to produce enhancement in previous investigations was present in each precursor location. However, the perceptual location of the precursor was different in every condition. Results from this investigation suggest that the perceived location of the precursor can have a significant effect on whether the precursor does or does not produce enhancement. If the perceived location of the precursor occurs in a different place from the simultaneous vowel stimulus, the precursor is not effective in enhancing the identification performance of the added vowel.