The effect of several factors upon voice identification was examined. These factors were: the size of the class of possible voices, the duration of the speech signal, the frequency range of the speech signal, voicingvsnonvoicing speech characteristics, and the simultaneous presentation of several voices. One of the most effective factors for speaker identification was the duration of the speech signal. Duration, as such, appears to be important, however, only insofar as it admits a smaller or larger statistical sampling of the speaker's speech repertoire.