While the auditory-only aspects of Mandarin speech are heavily-researched and well-known in the field, this dissertation addresses its lesser-known aspects: The visual and audio-visual perception of Mandarin segmental information and lexical-tone information. Chapter II of this dissertation focuses on the audiovisual perception of Mandarin segmental information. It strongly suggests that Mandarin speakers and English speakers are similar in their manner of audiovisual speech processing, despite differences in information across languages. It also strongly argues, along with previous research, that the McGurk-effect paradigm (although valuable in its own right) does not address the nature of information processing. Chapter III of this dissertation focuses on the visual perception of Mandarin segmental information. The synthetic visual speech of a computer-animated talking head was evaluated and subsequently improved. Also, the basic (or "minimum") units of Mandarin visual speech were determined for Mandarin initial-consonants and single-vowel endings. Although it may not be possible to completely standardize visual speech, at least some degree of standardization was achieved: The degrees of perceptual closeness among the items or categories were established. Chapter IV and Chapter V of this dissertation focus on the visual and audiovisual perception of Mandarin lexical tones. Under "ideal" conditions, there is visual tonal information, and it can influence tone-identification in the presence of ambiguous auditory tones. However, for naive or untrained participants, visual tonal information only had a slight (albeit statistically-significant) influence on tone-identification, and visual tones had no significant influences in the presence of clear auditory tones. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]