This project was undertaken to provide information about the sexual characteristics of preadolescent children's voices. In one series of experiments, perceptual judgments of sexual identity were obtained in response to 73 children's productions of isolated whispered and normally phonated vowels, normally spoken sentences, and sentences spoken in a monotonous fashion (Bennett and Weinberg, 1978). The purpose of this portion of the project was to describe certain acoustic and temporal characteristics of these children's speech samples, and to assess the relationship of these variables to perceptual judgments of sexual identity. Sexual differences in the frequency location of vocal tract resonances were significantly correlated with listener judgments of child sex in all four utterance conditions. The origin of the observed differences in vocal tract resonance characteristics is discussed with reference to possible sexual differences in vocal tract size as well as certain articulatory behaviors. Average fundamental frequency was significantly related to listeners' sex identifications in two utterance conditions. However, the influence of this variable was considerably less pronounced when compared to vocal tract information. Although certain measures of fundamental frequency variability (mean duration of level inflections and the rate of frequency change associated with upward shifts) were significantly related to perceptual measures of sexual identity, these cues were also interpreted to play a secondary role in defining maleness and femaleness in these children's voices.