The role of voice therapy in male-to-female transsexuals encompasses perceptual and acoustic analysis of voice characteristics and gathering of case history. The overall aim of therapy is to assist the male-to-female transsexual to achieve congruency between their gender identity and their presentation in the female role. Therapy goals have traditionally relied on varying empirical reports of gender differences in voice. Fundamental frequency (the acoustic correlate of pitch) is universally accepted as the voice feature that distinguishes males from females. However, increase in mean fundamental frequency to within the female range does not necessarily result in listener's perceptions of the speaker as female. Current research examines the voice characteristics that contribute to perceptions of gender, such as mean speaking fundamental frequency, the upper limit and lower limits of speaking fundamental frequency, intonation, resonance, and voice quality. This research demonstrates that these characteristics correlate—albeit in varying degrees—with perceptions of femininity.