According to Coleman (1971), "Differences in vocal pitch have been generally accepted as the acoustic cue that distinguishes between male and female speakers." A speaker's fundamental frequency is the primary determinant of the perceived pitch of his or her voice. The average fundamental frequency of the female voice is 260 Hertz and the average fundamental frequency of the male voice is 130 Hertz. "...a listener presumably makes a probability estimate of the speaker's sex based on the pitch of that particular voice as compared towhat he already knows about the pitch ranges of men and women." (Coleman, 1971) These presumptions, however, have been disputed by Coleman (1971, 1973), who found that removal of laryngeal cues, i.e., pitch cues, has little effect on the identification of the speaker's sex, especially with regard to the male voice.Part I of this study will attempt to further investigate Coleman's findings by having listeners decide whether a tape recorded voice (with laryngeal cue removed) is male or female. This will be accomplished by having a group of listeners identify the sex of four speakers from a tape recording of sentences produced by male and female speakers using an artificial larynx. Studies of Peterson and Barney (1952), Lehiste and Meltzer (1973), and others, have looked at the importance of formants in identifying spoken vowels. Ingemann (1968) and Schwartz and Rine (1968) have studied the ability of listeners to distinguish voiceless fricatives auditorily and have discussed the influence of the size of the vocal tract in the identification of voiceless fricatives.Part II of this study will attempt to determine if the size of the vocal tract in front of the constriction made in the formation of vowels has an influence on the accuracy of vowel identification. More specifically, an attempt will be made to determine whether or not, with the removal of normal laryngeal cues, back vowels are easier to recognize than front vowels in isolation, and which vowels are of greatest assistance in identification of the speaker's sex. This will be accomplished by having a group of listeners identify the vowel being said and the sex of the speaker from a tape recording of isolated vowels produced by male and female speakers using an artificial larynx.