While much of the existing literature on code-switching focuses on languages that differ typologically, this dissertation focuses on typologically similar languages. Code-switching between Mandarin and Taiwanese is examined through the perspectives of 1) sociolinguistics, 2) typology, 3) phonetic and phonological production, and 4) speech perception. Sociolinguistically, a questionnaire that examined usage domains and sociolinguistic perception revealed that Mandarin-Taiwanese code-switching is predominantly used in informal situations with social equals. Moreover, despite Taiwanese being a low-prestige language in Taiwan, Mandarin-Taiwanese code-switching is perceived positively and associated with solidarity. For the typological and phonetic/phonological investigations, a Mandarin-Taiwanese bilingual corpus containing approximately 11.6 hours of spontaneous speech was built. It was found that typologically, Mandarin-Taiwanese code-switching patterns can be affected by the sociolinguistic standings of the languages, the lexical gaps in the languages, a speaker's language dominance level, and the dominant language of the conversation. For the phonetic and phonological analyses, the production of Mandarin Tone 3 (T3) at code-switching boundary was examined to determine if speech production is affected by the relative level of language activation. On the phonetic level, code-switching boundary T3 contour is reduced when using monolingual language mode (i.e., speaking monolingually), and shows more variability when using bilingual language mode (i.e., speaking bilingually), suggesting a difference in language activation patterns in the code-switching in monolingual vs. bilingual language modes. On the phonological level, cross-language Mandarin T3 sandhi is more rule-governed when Mandarin is the matrix language of the code-switching utterance, revealing higher phonological control of sounds from the language at a higher level of activation. For the perception examination, a reaction time experiment was conducted to explore the perceptual cues of Mandarin-Taiwanese code-switching on the code-switched word. The results show that Mandarin-Taiwanese bilinguals are more sensitive to language-specific phonetic properties that occur earlier in the word, i.e., onset and nucleus. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]